Question

what Should be added to both 12 and 21 they So they are in the ratio 5:8​

Answer 1

Answer: add 3 to both 12 and 21.

Step-by-step explanation:

1. Find the common difference between the numbers

$\frac{12+d}{21+d} =\frac{5}{8}$

2. Cross multiply

8(12+d)=5(21+d)

expand: 96+8d=105+5d

3. Rearrange terms

8d-5d=105-96

3d=9

d=3

4. State response

the common difference is 3. To find what should be added to both 12 and 21, add 3.

12+3=15

21+3=24

This puts them in the ratio of 5:8

Hope this helps! :)

Answer 2

Answer:

$3$

Step-by-step explanation:

$\text{Solution:}\\\text{Let }x\text{ is the required number to be added to both 12 and 21 to make the }\\\text{ratio 5 : 8.}\\\text{Then,}\\\\\dfrac{12+x}{21+x}=\dfrac{5}{8}\\\\\text{or, }8(12+x)=5(21+x)\\\\\text{or, }96+8x=105+5x\\\\\text{or, }3x=9\\\\\text{or, }x=3$