Random Puzzles 

Workings

Hint
Loot at each number backwards.

Answer
32.

The first nine prime numbers reversed.

Workings

Hint
Start with the three connected squares that contain the third column on the bottom row.

Answer
 

Workings

Hint
Adding 900,000 to the number is the same as placing a 9 at the beginning.

Answer
23,076.

Reasoning
Placing the 9 at the beginning is equivalent to adding 900,000 (for example, 12,345 + 900,000 becomes 912,345).

Placing the 9 at the end is equivalent to multiplying by 10 and adding 9 (for example, 12,345 x 10 + 9 becomes 123,459).

Let's call the unknown number k, and we know that one of these numbers is 4 times the other, so:

 k + 900,000 = 4 x (10k + 9)

 k + 900,000 = 40k + 36

900,000 − 36 = 40k − k

     899,964 = 39k

899,964 ÷ 39 = k

Therefore, k = 23,076.

Double-Checking
923,076 = 4 x 230,769.

Workings

Hint
A little algebra might help.

Answer
I asked for 7 feet, 4 inches, but Alex brought me 4 feet, 7 inches.

Reasoning
If we label what I asked for as A feet and B inches, which is (12 x A + B) inches, then I actually received B feet and A inches, which is (12 x B + A) inches. Which means that:

   ⁵/₈ x (12 x A + B) = (12 x B + A)

Simplifying gives:

   A = ⁹¹/₅₂ x B

As B is the number of inches, it can only be between 1 and 12 and must give A as a whole number of feet.

B = 4 is the only possible value, which means that A = 7.

So I originally asked for 7 feet, 4 inches.

Double-Checking
I received 4 feet, 7 inches = 55 inches.

I asked for 7 feet, 4 inches = 88 inches, and 88 x ⁵/₈ = 55.