Video Transcript
Estimating Multiplication
Products
In this video, we will learn how to
estimate the products of two numbers including decimals by first rounding. Let’s practice with an example
question. We can estimate products by
rounding each number to its greatest place value as in the example.
Estimate 267 multiplied by
0.19.
Step one, identify the greatest
place value in each number. The greatest place value in the
number 267 is the two, worth two hundreds. And the greatest place value in
0.19 is the one, which is worth one tenth. Step two, round and multiply, 267
rounded to the nearest hundred is 300. 0.19 rounded to the nearest tenth
is 0.2. 300 multiplied by 0.2 equals
60. Use this method to estimate the
following products, 86 multiplied by 0.328; 717 multiplied by 0.901.
Let’s start with 86 multiplied by
0.328. Step one, we need to identify the
greatest place value in each number. The greatest place value in 86 is
the digit eight, which is worth eight tens. So we need to round 86 to the
nearest ten. And the digit with the greatest
value in 0.328 is the three, which is worth three tenths. So we’re rounding this number to
the nearest tenth. 86 rounded to the nearest ten is
90. And 0.328 rounded to the nearest
tenth is 0.3.
Now, we’ve rounded. We can multiply, 90 by 0.3 which
equals 27. Next, we need to calculate 717
multiplied by 0.901. First, we identify the digit with
the greatest place value in 717, that’s the seven, which is worth seven
hundredths. And in 0.901, the greatest place
value digit is the nine, which is worth nine tenths. So we’re rounding to the nearest
hundred and to the nearest tenths.
717 to the nearest hundred is
700. And 0.901 to the nearest tenth is
0.9. 700 multiplied by 0.9 equals
630.
In this video, we’ve learned how to
estimate the product of two numbers including decimals by, first, identifying the
digit with the greatest place value in each number, then rounding and
multiplying.
