T he Main Challenge
Here’s seven tricky mental teasers to try:
- (18 – 5) – (7 – 17) = ?
- 128 + 294 = ?
- How many seconds are in a quarter-of-an-hour?
- How many degrees are in three-quarters of a circle?
- (16 – 8) × (13 – 8) = ?
- On four consecutive days, you spend £55, £74, £36 and £15. What is the average amount spent per day?
- What is 15% of £8?
The 7puzzle Challenge
The playing board of the 7puzzle game is a 7-by-7 grid containing 49 different numbers, ranging from 2 up to 84.
The 1st & 2nd rows contain the following fourteen numbers:
2 8 9 14 15 17 22 28 40 48 55 63 64 72
Which two numbers have a difference of 42?
The Lagrange Challenge
Lagrange’s Four-Square Theorem states that every positive integer can be made by adding up to four square numbers.
For example, 7 can be made by 2²+1²+1²+1² (or 4+1+1+1).
There are FOUR ways of making 107 when using Lagrange’s Theorem. Can you find them?
The Mathematically Possible Challenge
Using 1, 4 and 9 once each, with + – × ÷ available, which FOUR numbers is it possible to make from the list below?
5 10 15 20 25 30 35 40 45 50
#5TimesTable
The Target Challenge
Can you arrive at 107 by inserting 9, 10, 11 and 12 into the gaps on both lines?
- ◯×◯+◯–◯ = 107 (2 different ways!)
- ◯×◯+(◯–◯)³ = 107
Answers can be found here.
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