Random Puzzles 

Workings

Hint
Try saying the letters out loud.

Answer
E.

These are letters which all sound the same, bee, see, dee, ee, etc. All depending on how you pronounce Z (zee or zed), you can include this.

Workings

Hint
Try working backwards.

Answer
120 miles.

Reasoning
I now have 5 miles left to travel, so I must have travelled 5 miles yesterday.

At the end of Day 3, I had 10 miles left to travel, so I must have had 40 miles left at the start of the Day 3.

At the end of Day 2, I had 40 miles left to travel, so I must have had 60 miles left at the start of the Day 2.

At the end of Day 1, I had 60 miles left to travel, so I must have had 120 miles left at the start of the Day 1.

Double-Checking
On the Day 1, I travelled 60 miles, leaving 60 miles.

On Day 2, I travelled 20 miles, leaving 40 miles.

On Day 3, I travelled 30 miles, leaving 10 miles.

Yesterday, I travelled 5 miles, leaving 5 miles.

Workings

Hint
You might need an old calculator.

Answer
Coil.

Reasoning
This is the only word that cannot be spelled using a calculator.

For example, if you enter 376616 into an old-fashioned calculator, and look at the number upside down, you can read GIGGLE.
376616  = giggle
7105    = soil
57738   = bells
378806  = gobble
4506    = gosh
5508    = boss
3704    = hole
5355378 = blesses
coil    = N/A

Workings

Hint
Try writing the numbers as words.

Answer
21.

These are numbers ending in a vowel (AEIOU).