Random Puzzles 

Workings

Hint
The word FEBRUARY appears 21 times.

Answer
The word FEBRUARY appears 21 times.

Workings

Hint
The word begins with the letter A.

Answer
Arm.

Double-Checking
swarm army alarm farm warm

Workings

Hint
Fill the 9-litre container first.

Answer
Here are the contents of the containers after each stage:

A = 9 litres, B = 4 litres
A     B
9     0     fill A
5     4     fill B from A (leaving 5 litres in A)
5     0     empty B
1     4     fill B from A (leaving 1 litre in A)
1     0     empty B
0     1     fill B from A
9     1     fill A
6     4     fill B from A (only 3 more litres fit in B)
6     0     empty B

This leaves 6 litres in container A.

Workings

Hint
I bought at least 6 of each stamp.

Answer
Six lots of 4p, 7p, and 19p, and ten lots of 5p, and 12p.

Reasoning
For three denominations of stamps, I was asked to buy 6 of each, and for the other two denominations, I had to buy 10 of each.

So I had to buy at least 6 of all five denominations.

This would be for a total of 6 x (4 + 5 + 7 + 12 + 19) = 282p = £2.82.

The remaining 68p has to buy the remaining 8 stamps, 4 of each of the two remaining denominations.

If we just bought 1 of each of the two remaining denominations they would have cost 68 ÷ 4 = 17p.

So the two remaining denominations must have been 5p and 12p.

Double-Checking
 6 x  4 =  24
10 x  5 =  50
 6 x  7 =  42
10 x 12 = 120
 6 x 19 = 114

For a total of 24 + 50 + 42 + 120 + 114 = 350p = £3.50.