Zara had 140 pens.
45 of them were white pens and the rest were black pens. After she had given away some white pens, the ratio of the number of white pens to the number of black pens became 3 : 4. How many white pens did she give away?
| |
White |
Black |
Total |
| Before |
4x4 =
16 u |
1x4 =
4 u |
5x4 =
20 u |
| Change |
- 13 u |
|
|
| After |
3 u |
4 u |
7 u |
The number of black pens remained unchanged.
LCM of 1 and 4 = 4
Total number of pens at first = 20 u
20 u = 140
1 u = 140 ÷ 20 = 7
Number of white pens that she gave away
= 16 u - 3 u
= 13 u
= 13 x 7
= 91
Answer(s):91
