Working systematically

What is the largest number which, when divided into 1905, 2587, 3951, 7020 and 8725 in turn, leaves the same remainder each time?

Use the clues to work out which cities Mohamed, Sheng, Tanya and Bharat live in.

Can you select the missing digit(s) to find the largest multiple?

You have two egg timers. One takes 4 minutes exactly to empty and the other takes 7 minutes. What times in whole minutes can you measure and how?

My cousin was 24 years old on Friday April 5th in 1974. On what day of the week was she born?

Can you arrange the digits 1, 1, 2, 2, 3 and 3 to make a Number Sandwich?

Five numbers added together in pairs produce: 0, 2, 4, 4, 6, 8, 9, 11, 13, 15 What are the five numbers?

Is there an efficient way to work out how many factors a large number has?

Show there are exactly 12 magic labellings of the Magic W using the numbers 1 to 9. Prove that for every labelling with a magic total T there is a corresponding labelling with a magic total 30-T.

Find all the ways of placing the numbers 1 to 9 on a W shape, with 3 numbers on each leg, so that each set of 3 numbers has the same total.