Evaluate correct to 4 decimal places 827.51 x 0.015

What is the area between two concentric circles of diameters 26cm and 20cm?

Marks scored by some children in an arithmetic test are:5, 3, 6, 9, 4, 7, 8, 6, 2, 7, 8, 4, 5, 2, 1, 0, 6, 9, 0, 8.
The arithmetic mean of the marks is

The weights of 30 new-born babies are given as follow: 6, 9, 5, 7, 6, 7, 5, 8, 9, 5, 7, 5, 8, 7, 8, 7, 5, 6, 5, 7, 6, 9, 9, 7, 8, 8, 7, 8, 9, 8. The mode is

If \(\sin x° = \frac{a}{b}\), what is \(\sin (90 - x)°\)?