Count all the parts
A ratio of 2:3 means the first amount has two equal parts and the second has three. Together they have 2 + 3 = 5 parts.
If the total is 20, each part is 20 ÷ 5 = 4. The first amount is 2 × 4 = 8. Its share of the whole is 2/5, because the whole includes both amounts.
Share 35 in the ratio 3:2
Divide a total of 35 in the ratio 3:2. The five parts are equal, so one part is 35 ÷ 5 = 7.
The first amount is 3 × 7 = 21 and the second is 2 × 7 = 14. Check both conditions: 21 + 14 = 35, and 21:14 simplifies to 3:2.
Use a new ratio
Now divide 40 in the ratio 3:5, first amount to second amount. Find the first amount.
Count the parts in the whole before dividing. The second ratio term counts the second amount’s parts; it does not count all the parts.
Try it
What is the first amount when 40 is divided in the ratio 3:5?
- 15
- 24
Show the answer
15
Yes. There are 3 + 5 = 8 parts. One part is 40 ÷ 8 = 5, so the first amount is 3 × 5 = 15.
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