Which of the following proportions is false?

10/25=40/100

18/48=20/50

25/45=75/135

24/30=20/25

Hey friend in order to figure that out, we need to solve all of these proportions.

Lets start with A!

What you first want to do is cross multiply so ...

10 * 100 = 25 * 40

Simplify

1000 = 25 * 40

1000 = 1000

Add - 1000 to both sides

1000 - 1000 = 1000 - 1000

0 = 0. (This proportion is true)

Moving on to B

Same steps!

18 * 50 = 48 * 20

900 = 48 * 20

900 = 960 (This is false therefore B is our answer however we want to check the others as well)

C is ...

25 * 135 = 45 * 75

3375 = 45 * 75

3375 = 3375

3375 - 3375 = 3375 - 3375

0 = 0 (True)

D is ...

24 * 25 = 30 * 20

600 = 30 * 20

600 = 600

600 - 600 = 600 - 600

0 = 0 (True)