Question

If 120% of a is equal to 80% of b, and a=12, then what is the value of a+b?

Answer 1

So,

120% is the same as 1.2 or 6/5. 80% is the same as 0.8 or 4/5.

We are given the value of a, which is 12.

6/5 of a, or 1.2 times a, is equal to 4/5 of b, or 4/5 times b.


`(6)/(5) (12)= (4)/(5) b`

Simplify.


`(72)/(5)= (4)/(5) b`

Multiply both sides by 5/4.


`(72)/(4)\ or\ 18= b`

Therefore, the sum of a and b is 12 + 18 = 30.

Answer 2

percent means parts out of 100
120%=120/100=1.2
80%=80/100=0.8
'of' means multiply

1.2 times a=0.8 times b
a=12
1.2 times 12=0.8 times b
14.4=0.8 times b
divide both sides by 0.8
18=b

so
a=12
b=18
a+b=12+18=30