Barbie is thinking of a number. Twenty less than one-third of the number is 72. What is Barbie's number?

I know that this is an easy equation but I keep on ending up with 236 as my answer. Help? Please include work on the problem

4 Answers
Jan 29, 2018

276

Explanation:

Let the number be x

Then, 1/3x-20 = 72

or, 1/3x = 72+20

or, 1/3x = 92

or, x = 92xx3 = 276

Let the number Barbie is thinking of be x

x/3 -20 =72

solve for x

Explanation:

x/3 -20 = 72

add 20 to each side

x/3=92

multiply both sides by 3

x = 276

Jan 29, 2018

x=276

Explanation:

All right. Let's write an equation.

"Twenty less than one-third of the number is 72"

Using x as the number, the sentence is equivalent to

x/3-20=72

We add 20 on both sides.

=>x/3-20+20=72+20

=>x/3=92 We now multiply both sides by 3.

=>(x/3)3=92*3

=>x=276

That is our answer!

I think that you did something like this:

x/3-20=72

x-20=216

=>x=236

This would not be true because when you multiply both sides by 3, you would get:

3(x/3-20)=72*3 Distribute.

=>x-60=216

=>x=276

We still get the same answer.

Jan 29, 2018

Barbie's number is 276, see below:

Explanation:

1/3*x-20=72

1/3*xcancel(-20+color(red)(20))=72+color(red)(20)

1/3*x=92

cancel(1/3)*x*cancel(color(red)(3))=92color(red)(*3)

x=276