Daily Practice - Higher Plus

A bag holds 5 counters, r of them red. Two are taken without replacement and P(both red) = 3/10. Work out r.

A histogram has four 10-wide classes from 0, with frequency densities 0.5, 2, 3, 1. Which class contains the median?

Expand and simplify (6 + √6)(6 - √6).Expand and simplify (6 + sqrt(6))(6 - sqrt(6)).

Solve x² + y² = 169 and y = x - 7 simultaneously.Solve x^2 + y^2 = 169 and y = x - 7 simultaneously.

y is directly proportional to √x. When x = 25, y = 15. Work out y when x = 64.y is directly proportional to sqrt(x). When x = 25, y = 15. Work out y when x = 64.