Higher Plus

A bag holds 11 counters, r of them red. Two are taken without replacement and P(both red) = 28/55. Work out r.

A histogram has four 20-wide classes from 0, with frequency densities 1, 0.5, 2, 3. Which class contains the median?

A block has mass 380 g (to the nearest 10 g) and volume 20 cm³ (to the nearest cm³). Work out the upper bound of its density, to 2 decimal places.A block has mass 380 g (to the nearest 10 g) and volume 20 cm^3 (to the nearest cm^3). Work out the upper bound of its density, to 2 decimal places.

Solve x² + y² = 225 and y = x + 3 simultaneously.Solve x^2 + y^2 = 225 and y = x + 3 simultaneously.

y is directly proportional to x. When x = 9, y = 21. Work out y when x = 16.y is directly proportional to sqrt(x). When x = 9, y = 21. Work out y when x = 16.