How to solve equations with decimals

An equation with decimals works the same way as one with integers, but we can make the arithmetic easier before we solve. We’ll pick a power of 10 that clears every decimal and multiply both sides by it.

Choose the power of 10 using place value

Find the decimal that goes farthest to the right. If it ends in the tenths place, multiply both sides by 10. If it ends in the hundredths place, multiply by 100. For thousandths, use 1,000. Multiplying both sides by the same nonzero number keeps the equation equivalent, and the distributive property applies that multiplier to each term.

Example: Clear a decimal in the tenths place

In 0.3x+5=11, the only decimal goes to the tenths place. Multiply both sides by 10.

10(0.3x+5)=10(11)3x+50=1103x=60x=20

Check in the original equation: 0.3(20)+5=6+5=11.

Example: Clear a negative decimal

In 6a+5a=-1.1, multiplying both sides by 10 clears the decimal on the right. The right side stays negative.

60a+50a=-11110a=-11a=-11110=-0.1

Example: Clear decimals with different place values

In 0.4n+3.9=5.78, the left side goes to the tenths place and the right side goes to the hundredths place. Multiplying by 100 turns all three numbers into integers.

100(0.4n+3.9)=100(5.78)40n+390=57840n=188n=18840=4.7

To check, substitute 4.7 for n. The left side gives 0.4(4.7)+3.9=1.88+3.9=5.78, which matches the right side.