2.
The letters in the top line are made exclusively of straight lines, whereas the letters in the bottom line are made of at least one curved line.
Accordingly, letters that can be added to the top line include E F I L M N V W X and Y.
Letters which can be added to the bottom line are B D O P Q and S.
3.
Fill the 3-litre bucket and pour the contents into the 5-litre bucket. Refill the 3-litre bucket and pour 2 litres into the 5-litre bucket (to fill it.) Empty 5-litre bucket. Pour the remaining 1 litre of water from 3-litre bucket into 5-litre bucket. Refill 3-litre bucket and empty all contents into 5-litre bucket to supply it with exactly 4 litres of water.
Total amount of water used is 3 + 3 + 3 = 9 litres.
4.
There are thirty (30) square shapes in this diagram.
5.
The letter E.
It is used to spell YEAR, WEEK, but not DAY.
6.
Add the letter A to ARE (one-syllable), and you get AREA (which has three syllables.)
7.
Neither, as roosters don’t lay eggs.
8.
There are thirty-eight (38) triangle shapes in this diagram.
9.
The arrow costs 50 cents.
The bow costs $20.50, which is $20.00 more than the arrow.
10.
White.
It is a polar bear (the house is situated on the North Pole.)
11.
Once you think outside the box (of the nine dots,) the solution is pretty simple.
12.
Place three balls on each side of the scales. If they are balanced, then use the scales for a second time to identify which of the two remaining balls is the heaviest. However, if one set of the three balls is heavier (on the first use of the scales,) take any two of these three balls and set them on the scales. If they are balanced, the third ball is the heaviest. Or, if one of these two balls is heavier, you have your answer.
13.
This is the simplest way to add two squares to separate all 9 dots.