Percents

Question 1

13 is what % of 25?

Answer 1

13 is 52% of 25

13/25 = x/100
Cross multiply
13*100=1300
1300/25 = 52

Question 2

50% of what is 290?

Answer 2

50% of 580 is 290

290(part)/(whole-?) = 50percent/100

Question 3

How to calculate percent change

Answer 3

Increase (or decrease) = (change / original) * 100

Question 4

You can want to buy a pair of pants that cost $100, but too expensive. Finally, it goes on sale for $60. What is the percent decrease?

Answer 4

40%

Formula for change
(Change/original) *100

(40/100)100= (0.4)100= 40%

Question 5

Jake makes $60 a week. He earns a raise and now makes $70 a week. What percent raise did he receive?

Answer 5

16.66%

Increase= (10/60)100= (1/6)100=16.66%

Question 6

Two years ago, the population of a street in Los Angles was 250. Last year, the population increased by 20% and this year the population is expected to increase another 10% in that street. How many residents is that street of Los Angles expected to have at the end of this year?

Answer 6

330.
First- Los Angles starts out with a population of 250. In the first year, the population increases by 20%, so we add 50 people (practice Fast Math here: 10% + 10% = 20%, so 25 + 25 = 50).
Our new population is 250 + 50 = 300. This year, Los Angles will add 10% but, this time, 10% is based on the new population figure of 300, not the old figure 250. This year, we add 30 people, so our population at the end of the year is expected to be 300 + 30 = 330.

Question 7

What is 60% of 320?

Answer 7

192

Trick:
60% = 50% + 10%
50% of 320 = 160
10% of 320 = 32
160 + 32 = 192

Question 8

What is 75% of 880?

Answer 8

660

Trick: break up into 50% + 25%
50% of 880 = 440
25% (or half of 50%) of 880 = 220
220+440= 660

Question 9

95% of 2400

Answer 9

2280

Break into parts:
100% and 5%
100% of 2400 = 2400
5% ( just take 10% and divide by 2)
Aka 10% of 2400 = 240 /2=120

2400 - 120= 2280

Question 10

16% of 42

Answer 10

6.72

10% + 5% + 1%
I.e. 4.2 + 2.1+ .42= 6.72

Question 11

Divide the mixed numbers

5 3/4 divided by 8 9/10

Answer 11

115/178

To solve- start by converting mixed numbers into fractions
5 3/4 --> 23/4
8 9/10 --> 89/10
Next invert the second fraction 
89/10 -> 10/89
Then multiply numerators 
10*23= 230
Then multiply denominators 4*89=356
Combine and simplify: 230/356>> (divided by 2)
115/178