Risa had some chikoo and starfruit face masks.
14 of them were chikoo. She gave away
15 of the chikoo face masks and
15 of the starfruit face masks. In the end, she had 128 chikoo and starfruit face masks altogether. How many starfruit face masks did Risa have at first?
| |
Chikoo face masks |
Starfruit face masks |
Total |
Comparing chikoo and starfruit face masks
at first |
1x5 =
5 u |
3x5 =
15 u |
4x5 =
20 u |
Before |
5 u |
5x3 =
15 u |
|
Change |
- 1 u |
- 1x3 =
- 3 u |
|
After |
4 u |
4x3 =
12 u |
|
The number of starfruit face masks at first is repeated. Make the number of starfruit face masks the same. LCM of 3 and 5 is 15.
Total number of face masks in the end
= 4 u + 12 u
= 16 u
16 u = 128
1 u = 128 ÷ 16 = 8
Number of starfruit masks at first
= 15 u
= 15 x 8
= 120
Answer(s): 120
