PSLE Ivan had a total of 120 blue and red pens. After selling an equal number of both types, he had
25 of the blue pens and
45 of the red ones left. What was the total number of pens sold?
Fraction of the blue pens sold
= 1 -
25 =
35 Fraction of the red pens sold
= 1 -
45 =
15 The number of blue pens and red pens sold is the same.
Make the numerators the same.
LCM of 3 and 1 = 3
35 Long pens =
15 Short pens
3x15x1 Long pens =
1x35x3 Short pens
35 Long pens =
315 Short pens
|
Long |
Short |
Total |
Before |
5 u |
15 u |
20 u |
Change |
- 3 u |
- 3 u |
- 6 u |
After |
2 u |
12 u |
14 u |
Total number of pens at first
= 5 u + 15 u
= 20 u
20 u = 120
1 u = 120 ÷ 20 = 6
Total number of pens sold
= 3 u + 3 u
= 6 u
= 6 x 6
= 36
Answer(s): 36