Random Puzzles 

Workings

Hint
I bought at least 8 of each stamp.

Answer
Eight lots of 11p, 17p and 21p, and nine lots of 3p and 9p.

Reasoning
For three denominations of stamp I was asked to buy 8 of each, and for the other two denominations I had to buy 9 of each.

So I had to buy at least 8 of all five denominations.

This would be for a total of 8 x (3 + 9 + 11 + 17 + 21) = 488p = £4.88.

The remaining 12p has to buy the remaining 2 stamps, which must have been 3p and 9p.

Double-Checking
9 x 3 = 27
9 x 9 = 81
8 x 11 = 88
8 x 17 = 136
8 x 21 = 168

For a total of 27 + 81 + 88 + 136 + 168 = 500p = £5.

Workings

Answer
Fred, Darren, Nick.

Workings

Hint
There are 3 feet in a yard, 1760 yards in a mile, and 8 furlongs in a mile.

Answer
Square feet in half a square mile.

Reasoning
There are 3 feet in a yard, 1760 yards in a mile, and 8 furlongs in a mile.

A mile is 1760 x 3 = 5280 feet in a mile.

A square mile is 5280 x 5280 = 27878400 square feet.

Therefore, half a square mile = 13,939,200 square feet.

A furlong is 1760 ÷ 8 = 220 yards.

Therefore, a cubic furlong is 220 x 220 x 220 = 10,648,000 cubic yards.

Workings

Hint
Try removing the spaces.

Answer
rf.

This sequence spells out the numbers onetwothreefourfive etc.