Question

Use the example below to explain where the decimal point should be placed in the product. Next, explain how estimation can be used to check your answer.

Ex: 25.5 x 0.81 =

Answer 1

20.655

Explanation:

25.5*0.81 =

Estimation: ROUND UP 26*1

26*1 > 25.5*0.81

When multiplying, ignore the decimal points.

255*81= 20655

In 25.5, the decimal point is one place to the left. In 0.81, the decimal place is two places to the left. One plus two is three. So 3 places to the left of 20655 is 20.655. The answer is 20.655

Answer 2

When multiplying numbers with decimals, you move the decimal point to the left the quantity of numbers there are to the right of the decimals in the equation.

In 25.5 there is 1 number to the right of the decimal point and in 0.81 there are 2 numbers to the right of the decimal point, so after multiplying you would move the decimal 3 places to the left.

25.5 x 0.81 = 20.655 ( note there are 3 numbers to the right of the decimal point)