Topic: Off-topic /
Math riddle thingy!

OK, I shall now post a few puzzles.

1. Can you write down a straight forward subtraction sum, a – b = c, where each of the numbers (a, b and c) is made up of the nine digits, 1-9 inclusive, with each digit being used once only in each number?

2. If a clock takes 2 seconds to strike 2 o’clock, how long will it take to strike 3 o’clock? (do not include the 1 hour)

3. If a man walks due south for 4 miles and then due north for 3 miles, what is the maximum distance he can be from where he started?

4. What do you think should come next in each sequence and why?

a) 4, 6, 26, 666

b) 22, 20, 10, 8, 4, 2

c) 2, 4, 13, 26, 35, 70

d) 5 1/5, 4 1/4, 3 1/3, 2 1/2

e) 4, 5, 7, 9, 13, 15, 19, 21

f) 1, 9, 1, 4, 1, 9, 1, 8, 1, 9, 3, 9, 1, 9, 4

g) 166.6666…, 187.5, 214.28571…, 250, 300

h) 4, 8, 32, 512, 131072

i) 4, 6, 8, 9, 10, 12, 14, 15, 16

5. At any gathering where more than two people are present, there will be at least two people who have exactly the same number of friends present. True or false? Explain.

6. Use three identical digits in a simple addition sum so that the total is 12. You cannot use the digit 4.

7. Professor Boffin has discovered an exciting mathematical phenomenon concerning fractions with digits under 100. If he cancels Identical digits above and below the line, the fraction is still correct. e.g. 16/64 = 1/4 Can you find three other proper fractions of which this is true?

8. Mary was meant to proofread a document at the rait of 30 pages a day. Lazy Mary was half way through the document before she realised that she was only working at the rate of 15 pages a day. How fast does she need to proof-read the rest of the document in order to reach her target of 30 per day.