Multiplication of decimals

Multiplication of decimals

When multiplying decimals, follow the same procedure used when multiplying whole numbers. Count the required number of decimal places from the right of the product obtained. The number of decimal places in the answer is obtained by counting the total number of decimal places from the multiplied decimals.

Multiplying decimals with two decimal places by decimals with one decimal place

(a) $4.52 \times 1.3 =$

Solution

The number $4.52$ has two decimal places and $1.3$ has one decimal place. This gives a total of three decimal places.

Multiply these numbers as whole numbers without considering their decimal places. That is, multiply $452$ by $13$ then count three decimal places from right to left of the answer as follows:

    452
  ×  13
   ────
   1356
 + 4520
   ────
   5876

After counting three decimal places, the answer is $5.876$.

Therefore, $4.52 \times 1.3 = 5.876$

(b) $100.55 \times 0.2 =$

Solution

Multiply $10{,}055$ by $2$, then indicate three decimal places as follows:

  10055
×    2
──────
  20110

After counting three decimal places, the answer is $20.110$.

Therefore, $100.55 \times 0.2 = 20.110$