Betty had 1700 mℓ more coffee than Rachel. After Betty gave Rachel 400 mℓ of coffee, the ratio of Betty's coffee to Rachel's coffee became 7 : 4. How much coffee did Betty have at first? Give your answer in millilitres.
| |
Betty |
Rachel |
Difference |
| Before |
1 u + 1700 |
1 u |
1700 |
| Change |
- 400 |
+ 400 |
|
| After |
1 u + 1300 |
1 u + 400 |
900 |
Comparing Betty and
Rachel in the end |
7 p |
4 p |
3 p |
Volume of coffee that Betty had in the end
= 1 u + 1700 - 400
= 1 u + 1300
Difference in the volume of coffee between Betty and Rachel in the end
= 7 p - 4 p
= 3 p
3 p = 1300 - 400
3 p = 900
1 p = 900 ÷ 3 = 300
Volume of coffee that Betty had at first
= 7 p + 400
= 7 x 300 + 400
= 2100 + 400
= 2500 mℓ
Answer(s): 2500 mℓ
