Risa had 1700 mℓ more coffee than Marion. After Risa gave Marion 490 mℓ of coffee, the ratio of Risa's coffee to Marion's coffee became 7 : 3. How much coffee did Risa have at first? Give your answer in millilitres.
|
Risa |
Marion |
Difference |
Before |
1 u + 1700 |
1 u |
1700 |
Change |
- 490 |
+ 490 |
|
After |
1 u + 1210 |
1 u + 490 |
720 |
Comparing Risa and Marion in the end |
7 p |
3 p |
4 p |
Volume of coffee that Risa had in the end
= 1 u + 1700 - 490
= 1 u + 1210
Difference in the volume of coffee between Risa and Marion in the end
= 7 p - 3 p
= 4 p
4 p = 1210 - 490
4 p = 720
1 p = 720 ÷ 4 = 180
Volume of coffee that Risa had at first
= 7 p + 490
= 7 x 180 + 490
= 1260 + 490
= 1750 mℓ
Answer(s): 1750 mℓ