12½% is 1/8

To find 12½% of a number divide by 8.

12½% = 12.5% =

By Jim Olsen, W.I.U.#P13

1

8

1

8

5

8

2

8

8

8

7

8

6

8

4

8

3

8

9

8

0

81

4

3

4

1

20 1

0% 12.5% 25% 37.5% 50% 62.5% 75% 87.5% 100% 112.5%

12½¢12½¢12½¢12½¢12½¢12½¢12½¢

12½¢ $1.00

25¢

25¢

25¢

25¢ $1.00

Historical NoteIn colonial times, a common coin was the Spanish dollar. It was often cut in halves, quarters, and eighths. One-eighth was one bit, or 12½¢.Two bits was a quarter or 25¢.

Find the percent

1. $1000 is what percent of $8000?

2. 9 misses out of 24 attempts is what percent?

12

9 337 % missed

24 8

12

1000 112 %

8000 8

Recall the strategy:To find A% of BYou can change the percent to a fraction,Find B divided by the bottom, thenMultiply by the top.

Find 37 ½ % of 32

12

3 3237 % of 32 32 3 4 3 12

8 8

Here’s one that looks hard, but is quite easy if you know the strategy!

Find the number

1. Find 87.5% of 40.

2. Find 112.5% of 560.

3. Find 37.5% of 8000.

7 of 40 (40 8) 7 5 7 35

8

9112.5% of 560 of 560 (560 8)*9 70*9 630

8

3 of 8000 1000*3 3000

8

Examples:

1. The total bill was $320. Utilities are 12.5%. How much were utilities?

2. If Jennifer wants 37.5% of her investments in stocks and plans to invest $4,800, how much will she invest in stocks?

2. If 62.5% of the voters were against the proposal and 720 people voted, how many were against the proposal ?

3. If Jamal got 9 correct on the quiz which had 8 questions (because he got the extra credit, challenge question right), what was his percent?

34800 (4800 8) 3 600 3 $1,800

8

5 720 of 720 5 90 5 450

8 8

9112.5%

8

1 320 of 320 $40

8 8

Closing Notes

Remember

12½% is 1/8 To find 12½% of a number divide

by 8.

#P13

RecapHere are the percents we know so far.

Fraction Percent1/2 50 %1/3 33⅓ %1/4 25 %1/5 20 %1/8 12½ %