The back-to-back stem-and-leaf diagram shows the annual salaries of 19 employees at each of two companies, Petral and Ravon. Petral 30 | 0 0 3 31 | 1 2 2 8 9 9 32 | 0 4 5 5 33 | 3 5 7 34 | 0 1 35 | 3 36 | 8 Ravon 30 | 2 6 31 | 1 5 32 | 0 0 2 33 | 0 4 8 9 34 | 1 1 3 4 6 35 | 3 36 | 7 9 Key: 2|31|5 means $31200 for a Petral employee and $31500 for a Ravon employee. The median salary of the Ravon employees is $33800, the lower quartile is $32000 and the upper quartile is $34400.

Last Saturday, Sarah recorded the colour and type of 160 cars in a car park. All the cars that were not red or silver...

The discrete random variable X has the following probability distribution. X|-2|0|1|3|4 P(X = x)|0.2|0.1|p|0.1|q

A summary of n values of x gave the following information: Σ(x – 20) = 136, Σ(x – 20)² = 2888. The mean of the n valu...

The parametric equations of a curve are x = 2t + sin 2t, y = 1 – 2 cos 2t, for −½π < t < ½π.

The variables x and θ satisfy the differential equation x cos² θ (dx/dθ) = 2 tan θ + 1, for 0 ≤ θ < ½π and x > 0. It ...