There are 200 balls in a basket. 0.2 of them are white balls, and the rest are red and black balls. If there are 17 as many red balls as black balls. How many black balls are there?
| White balls |
Red balls |
Black balls |
Total |
| 1 u |
4 u |
5 u |
| |
1 p |
7 p |
|
0.2 =
210 =
15 Fraction of balls that are red and black balls
= 1 -
15 =
45 Total number of balls = 5 u
5 u = 200
1 u = 200 ÷ 5 = 40
Number of red balls and black balls
= 4 u
= 4 x 40
= 160
Number of red and black balls
= 1 p + 7 p
= 8 p
8 p = 160
1 p = 160 ÷ 8 = 20
Number of black balls
= 7 p
= 7 x 20
= 140
Answer(s): 140
