14 Divisors

What is the smallest number with exactly 14 divisors?

Summing Consecutive Numbers

Many numbers can be expressed as the sum of two or more consecutive integers. For example, 15=7+8 and 10=1+2+3+4. Can you say which numbers can be expressed in this way?

Dozens

Do you know a quick way to check if a number is a multiple of two? How about three, four or six?

Weekly Problem 22 - 2011

Stage: 3 Short Challenge Level:

Sarah goes up a hill and then down again the same way. On the way up she averages $2$ miles per hour. On the way down she averages $4$ miles per hour. What is Sarah's average speed in miles per hour for the whole journey? Give an exact answer.

If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.

This problem is taken from the UKMT Mathematical Challenges.

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