Kathy had 2180 mℓ more coffee than Winnie. After Kathy gave Winnie 550 mℓ of coffee, the ratio of Kathy's coffee to Winnie's coffee became 7 : 3. How much coffee did Kathy have at first? Give your answer in millilitres.
| |
Kathy |
Winnie |
Difference |
| Before |
1 u + 2180 |
1 u |
2180 |
| Change |
- 550 |
+ 550 |
|
| After |
1 u + 1630 |
1 u + 550 |
1080 |
Comparing Kathy and
Winnie in the end |
7 p |
3 p |
4 p |
Volume of coffee that Kathy had in the end
= 1 u + 2180 - 550
= 1 u + 1630
Difference in the volume of coffee between Kathy and Winnie in the end
= 7 p - 3 p
= 4 p
4 p = 1630 - 550
4 p = 1080
1 p = 1080 ÷ 4 = 270
Volume of coffee that Kathy had at first
= 7 p + 550
= 7 x 270 + 550
= 1890 + 550
= 2440 mℓ
Answer(s): 2440 mℓ
