"USE YOUR BRAIN, NOT YOUR CALCULATOR." part 3

Here is a final group of mental math questions. In the near future, I will talk more in depth about the concept and use of "halfway numbers."

Mental Math

Mental Math # 11
8.What is two-thirds of four-fifths?
9.40 is what percent of 1O? Ten is what percent of forty?
10.How many thirds in 60?
11.8.4 /1000
12.163 cm is how many meters?
13.What is 15% of $12?

Mental Math #12
16.What is three-fourths of three-fourths?
17.One and one-half minus one-fourth?
18.How many quarts in 12 gallons?
19.If marbles are $1.20 per dozen, what is the cost of 3 marbles?
20.9 is what percent of 6? 6 is what percent of 9?
21.What is halfway between 490 and 522?
22.A trip lasted from 7:50 am to 2:05 pm. How long was the trip?
23.Which is better in percentage - making 8 out of 14 free throws or making 12 out of 25 free throws?

Mental Math #13
24.4.3+9.8
25.202-39
26.Round 68.561 to the nearest tenth.
27.Five minus one and seven-eights
28.9.6 / 1000
29.How many pints in one gallon?
30.What is four to the third power in factored form? Standard form?
31.What would be a 15% tip on a restaurant bill of $21.50?

Mental Math # 14
32.218 to the zero power equals what number?
33.What is one-half of seven eights?
34.What is 40% of 40?
35.Round 4.088 to the nearest tenth.
36.Eleven and one-fourth minus two and one-half.
37. 981-208.
38.A trip lasted from 9:45 am to 2:20 pm. How long is the trip?
39.Approximate a 15% tip on a restaurant bill of $26.49.

Mental Math #15
40.4 is what percent of 20?
41.20 is what percent of 4?
42.Two-fifths minus one third.
43.How many quarts are in two and one-half gallons?
44.$4.85 (10 000).
45.Two fifths minus one third.