What is the smallest number with exactly 14 divisors?
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?
If it takes four men one day to build a wall, how long does it take 60,000 men to build a similar wall?
Here is an alternative and more unusual version of the "Think of a Number" game which you may have heard of before.
Think of two whole numbers under $10$. Take one of them and add $1$. Multiply by $5$. Add $1$ again. Double your answer. Subtract $1$. Add your second number. Add $2$. Double again. Subtract $8$. Halve this number and tell me your answer.
From your answer I can work out both your numbers very quickly. How?
Try with different numbers until you see how it works and then you'll be ready to amaze your friends!
Click here for a poster of this problem.