Admissions tests / ESAT / Maths 1 / Geometry and measures
Test standard. 15 questions, 15 marks, about 22 minutes.
ESAT Mathematics 1: Geometry and measures, set 1
Angles and polygons, congruence and similarity, Pythagoras and trigonometry, circles and circle theorems, mensuration, transformations and vectors.
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- Answer all questions. No calculator allowed.
- Each question has exactly one correct answer.
- No diagrams are provided. Read each description carefully and, if it helps, sketch the shape yourself before answering.
- 11 mark
Three angles meeting at a single point are 3x degrees, 5x degrees and 4x degrees. Together they make a complete turn about that point. Find the value of x.
- 21 mark
A solid pyramid has a hexagonal base and six triangular faces that all meet at a single apex above the base. How many edges does the pyramid have in total?
- 31 mark
In kite ABCD, AB = AD and CB = CD, so the diagonal AC is a line of symmetry and angle ABC = angle ADC. Angle BAD = 80 degrees and angle BCD = 120 degrees. Find angle ABC.
- 41 mark
Triangle ABC has AB = 8 cm, angle A = 50 degrees and angle B = 70 degrees. Triangle DEF has DE = 8 cm, angle D = 50 degrees and angle E = 70 degrees. Which congruence criterion proves that triangle ABC is congruent to triangle DEF?
- 51 mark
Triangle ABC is similar to triangle PQR, with side AB corresponding to side PQ. AB = 6 cm, PQ = 9 cm, and the area of triangle ABC is 24 cm^2. Find the area of triangle PQR.
- 61 mark
Triangle ABC has vertices A(2,1), B(4,1) and C(2,5). The triangle is enlarged by scale factor -2 about the origin O. Find the coordinates of the image of point C.
- 71 mark
OABC is a parallelogram, with O at the origin. Vector OA = a and vector OC = c. M is the midpoint of side AB. Find vector OM in terms of a and c.
- 81 mark
Isosceles triangle ABC has AB = AC = 13 cm and base BC = 10 cm. Find the height from vertex A to the base BC.
- 91 mark
A cuboid has edges of length 3 cm, 4 cm and 12 cm. Find the length of the longest diagonal inside the cuboid, connecting two opposite corners.
- 101 mark
Points A, B and C lie on the circumference of a circle with centre O. The angle at the centre standing on arc AC, angle AOC, is 130 degrees, and B lies on the major arc. Find angle ABC, the angle subtended by the same arc AC at the circumference.
- 111 mark
AB is a diameter of a circle, and C is a point on the circumference such that AC = 6 cm and BC = 8 cm. Find the length of the diameter AB.
- 121 mark
A ship sails from port A on a bearing of 065 degrees to reach port B. Find the bearing of port A from port B (the back bearing).
- 131 mark
A sector of a circle has radius 9 cm and an angle of 40 degrees at the centre. Find the exact length of the arc, in terms of pi.
- 141 mark
A cylinder has radius 4 cm and height 10 cm. Find its volume in terms of pi.
- 151 mark
A right-angled triangle has a hypotenuse of length 12 cm and one angle of 30 degrees. Find the exact length of the side opposite the 30-degree angle.
Worked solutions
Every question below carries the reasoning, not just the answer. The official material for this test publishes a correct option letter and nothing else.
Question 1Answer: B
- The three angles lie all the way around a single point, so they must add up to 360 degrees, not 180 degrees (that rule is for a straight line).
- So 3x + 5x + 4x = 360, which simplifies to 12x = 360.
- Dividing both sides by 12 gives x = 30.
- Why not A: This comes from setting 3x + 5x + 4x equal to 180 degrees, the rule for angles on a straight line, rather than 360 degrees for angles at a point.
- Why not C: This comes from adding only two of the three terms, 3x + 5x = 8x, and forgetting the 4x term before dividing 360 by 8.
- Why not D: This comes from dividing 360 by 4 instead of by 12, miscounting the number of x-terms in 3x + 5x + 4x as four rather than three (3 + 5 + 4 = 12).
Question 2Answer: A
- The base is a hexagon, so it has 6 sides, and each side is an edge of the solid.
- Each of the 6 base vertices is also joined to the apex by a slant edge, giving 6 more edges.
- In total the pyramid has 6 + 6 = 12 edges.
- Why not B: This counts only the six edges running from the apex down to each base vertex, forgetting the six edges that form the hexagonal base itself.
- Why not C: This applies Euler's formula for a solid, faces + vertices - edges = 2, but adds faces and vertices together (7 + 7 = 14) instead of subtracting 2 from that total to isolate the edges.
- Why not D: This gives the number of faces (six triangles plus one hexagonal base = 7), mistaking a face count for an edge count.
Question 3Answer: C
- The angles of any quadrilateral add up to 360 degrees.
- So angle BAD + angle BCD + angle ABC + angle ADC = 360, giving 80 + 120 + angle ABC + angle ADC = 360.
- Because AC is a line of symmetry, angle ABC = angle ADC, so the remaining 160 degrees is split equally between them: angle ABC = 160 / 2 = 80 degrees.
- Why not A: This assumes all four angles of the kite are equal and divides 360 by 4, but a kite only has one pair of equal angles (at B and D), not four equal angles.
- Why not B: This finds the combined size of angles ABC and ADC together (360 - 80 - 120 = 160) but forgets to divide that total between the two equal angles.
- Why not D: This wrongly assumes angle ABC equals angle BCD, the adjacent angle at C, instead of angle ADC, the angle at D on the other side of the line of symmetry.
Question 4Answer: A
- The two given angles and the side between them are known in each triangle: angle A, side AB and angle B correspond to angle D, side DE and angle E.
- A known side lying between two known angles is the ASA condition: two angles and the included side.
- Since AB = DE, angle A = angle D and angle B = angle E, the ASA condition is satisfied, so the triangles are congruent by ASA.
- Why not B: SSS requires all three pairs of sides to be known equal, but only one pair of corresponding sides (AB and DE) is given here.
- Why not C: SAS requires two sides and the angle included between them, but only one side is given in each triangle, not two.
- Why not D: RHS requires a right angle and the hypotenuse, but no right angle is stated in either triangle.
Question 5Answer: D
- The linear scale factor from triangle ABC to triangle PQR is PQ / AB = 9 / 6 = 3/2.
- Areas of similar shapes scale with the SQUARE of the linear scale factor, so the area scale factor is (3/2)^2 = 9/4.
- The area of triangle PQR is therefore 24 x 9/4 = 54 cm^2.
- Why not A: This multiplies the area by the linear scale factor 9/6 = 3/2 directly (24 x 3/2 = 36), forgetting that area scales with the SQUARE of the linear scale factor, not the scale factor itself.
- Why not B: This cubes the linear scale factor instead of squaring it (24 x (3/2)^3 = 81), applying the rule for how VOLUME scales between similar solids rather than how area scales between similar shapes.
- Why not C: This uses the reciprocal of the scale factor without squaring it (24 x 2/3 = 16), the wrong direction and the wrong power for going from the smaller triangle to the larger one.
Question 6Answer: B
- An enlargement with centre the origin and scale factor k maps a point (x, y) to (kx, ky).
- Here k = -2 and C = (2, 5), so the image has coordinates (-2 x 2, -2 x 5).
- That gives the image of C as (-4, -10).
- Why not A: This uses scale factor +2 instead of -2, forgetting the negative sign, so the image lands on the same side of the centre as C rather than the opposite side.
- Why not C: This adds the scale factor -2 to each coordinate of C (2 + (-2), 5 + (-2)) as if the enlargement were a translation, rather than multiplying each coordinate by -2.
- Why not D: This multiplies only the x-coordinate of C by the scale factor and leaves the y-coordinate unchanged, instead of multiplying both coordinates.
Question 7Answer: C
- Since OABC is a parallelogram, side AB is equal and parallel to side OC, so vector AB = vector OC = c.
- The position vector of B is therefore OB = OA + AB = a + c.
- M is the midpoint of AB, so OM = OA + (1/2) x AB = a + (1/2)c.
- Why not A: This finds the midpoint of the whole diagonal OB (giving (a + c)/2) instead of the midpoint of side AB.
- Why not B: This uses the full vector OB = a + c, forgetting that M is the MIDPOINT of AB and not the vertex B itself.
- Why not D: This halves vector a but keeps vector c whole, the reverse of what is needed: it is the c-part of AB that should be halved, since AB itself equals vector c.
Question 8Answer: D
- The height from A meets BC at its midpoint, splitting the isosceles triangle into two congruent right-angled triangles, each with hypotenuse 13 cm and base 10 / 2 = 5 cm.
- By Pythagoras' theorem, height^2 = 13^2 - 5^2 = 169 - 25 = 144.
- So the height is sqrt(144) = 12 cm.
- Why not A: This applies Pythagoras' theorem using the full base of 10 cm as one side of the right-angled triangle (sqrt(13^2 - 10^2)), forgetting that the height splits the isosceles triangle into two right-angled triangles each with a base of only half of BC.
- Why not B: This subtracts half the base directly from the equal side (13 - 5 = 8) instead of using Pythagoras' theorem to combine them.
- Why not C: This adds the squares of 13 and 5 instead of subtracting them (sqrt(13^2 + 5^2)), the opposite of what Pythagoras' theorem requires for finding a shorter side from the hypotenuse.
Question 9Answer: A
- For a cuboid with edges p, q and r, the space diagonal has length sqrt(p^2 + q^2 + r^2), applying Pythagoras' theorem twice: once across a face, once through the solid.
- Here p = 3, q = 4 and r = 12, so the diagonal squared is 3^2 + 4^2 + 12^2 = 9 + 16 + 144 = 169.
- So the diagonal has length sqrt(169) = 13 cm.
- Why not B: This applies Pythagoras' theorem to only two of the three edges (sqrt(3^2 + 4^2) = 5), treating the problem as a 2-dimensional right-angled triangle and forgetting the third edge entirely.
- Why not C: This simply adds the three edge lengths together (3 + 4 + 12 = 19) instead of using the 3-dimensional form of Pythagoras' theorem.
- Why not D: This takes the square root of the SUM of the edge lengths (sqrt(3 + 4 + 12) = sqrt(19)) instead of the square root of the sum of their SQUARES.
Question 10Answer: B
- The angle subtended at the centre of a circle by an arc is always twice the angle subtended at the circumference by the same arc.
- Here angle AOC = 130 degrees is the angle at the centre standing on arc AC.
- So the angle at the circumference, angle ABC, is half of this: 130 / 2 = 65 degrees.
- Why not A: This gives the angle at the CENTRE itself (130 degrees) rather than halving it to find the angle at the circumference.
- Why not C: This doubles the centre angle instead of halving it (130 x 2 = 260), inverting the theorem's relationship between the two angles.
- Why not D: This subtracts the centre angle from 180 (180 - 130 = 50), applying the rule for opposite angles of a cyclic quadrilateral rather than the angle-at-the-centre theorem.
Question 11Answer: C
- The angle in a semicircle is always a right angle, so angle ACB = 90 degrees because AB is a diameter.
- Triangle ACB is therefore right-angled at C, with AB as the hypotenuse.
- By Pythagoras' theorem, AB^2 = AC^2 + BC^2 = 6^2 + 8^2 = 36 + 64 = 100, so AB = sqrt(100) = 10 cm.
- Why not A: This simply adds the two chord lengths together (6 + 8 = 14) instead of recognising that angle ACB = 90 degrees (the angle in a semicircle) and applying Pythagoras' theorem.
- Why not B: This multiplies the two chord lengths together (6 x 8 = 48), which is not a step in Pythagoras' theorem or any circle rule that applies here.
- Why not D: This takes half of the sum of the two given lengths (6 + 8 = 14, then 14 / 2 = 7), an average with no basis in Pythagoras' theorem or any circle theorem.
Question 12Answer: D
- A back bearing, the bearing measured in the opposite direction along the same line, differs from the original bearing by 180 degrees.
- Since the original bearing, 065 degrees, is less than 180 degrees, the back bearing is found by adding 180.
- So the bearing of A from B is 065 + 180 = 245 degrees.
- Why not A: This gives the original bearing unchanged (065 degrees), as if the bearing of A from B were simply the same as the bearing of B from A, forgetting that a back bearing points in roughly the opposite direction.
- Why not B: This subtracts the bearing from 360 (360 - 65 = 295), a rule for a different situation entirely, not for finding a back bearing.
- Why not C: This adds 90 degrees instead of 180 degrees (65 + 90 = 155), confusing the back-bearing rule with a right-angle turn.
Question 13Answer: A
- The arc length is the fraction of the full circumference that the sector's angle represents: (angle / 360) x 2 x pi x r.
- Here angle = 40 degrees and r = 9 cm, so the fraction is 40/360 = 1/9.
- The arc length is therefore (1/9) x 2 x pi x 9 = 2pi cm.
- Why not B: This uses the formula for the AREA of the sector (40/360 x pi x 9^2 = 40/360 x pi x 81 = 9pi) instead of the formula for the arc LENGTH, mixing up the two different formulae.
- Why not C: This treats 9 cm as the DIAMETER rather than the radius, halving it to 4.5 cm before applying the arc length formula (40/360 x 2 x pi x 4.5 = pi).
- Why not D: This uses 180 degrees as the full turn instead of 360 (40/180 x 2 x pi x 9 = 4pi), as if the sector were being compared to a semicircle rather than a whole circle.
Question 14Answer: B
- The volume of a cylinder is given by V = pi x r^2 x h, where r is the radius and h is the height.
- Here r = 4 cm and h = 10 cm, so r^2 = 16.
- The volume is therefore pi x 16 x 10 = 160pi cm^3.
- Why not A: This uses the formula for the CURVED SURFACE AREA of a cylinder (2 x pi x r x h = 2 x pi x 4 x 10 = 80pi) instead of the volume formula, mixing up area with volume.
- Why not C: This forgets to square the radius (pi x r x h = pi x 4 x 10 = 40pi) instead of using pi x r^2 x h.
- Why not D: This uses the DIAMETER squared in place of the radius squared (pi x 8^2 x 10 = 640pi), doubling the radius before squaring it instead of squaring the radius itself.
Question 15Answer: C
- For a right-angled triangle, sin(angle) = opposite / hypotenuse, so opposite = hypotenuse x sin(angle).
- The exact value of sin 30 degrees is 1/2, which candidates should know without a calculator.
- So the opposite side is 12 x 1/2 = 6 cm.
- Why not A: This uses cos 30 (= sqrt(3)/2) instead of sin 30, finding the ADJACENT side (12 x sqrt(3)/2 = 6 sqrt(3)) rather than the side opposite the 30-degree angle.
- Why not B: This divides 12 by sin 30 instead of multiplying (12 / (1/2) = 24), inverting the relationship between the hypotenuse and the opposite side.
- Why not D: This uses tan 30 (= 1/sqrt(3)) instead of sin 30, treating the hypotenuse as if it were the adjacent side in a tangent ratio (12 x 1/sqrt(3) = 4 sqrt(3)).
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