Video: AF5P1-Q05-859198167931

Calculate 1.4 × 3 − 2.4.


Video Transcript

Calculate 1.4 multiplied by three minus 2.4.

Whilst it might seem sensible to work from left to right in a calculation like this, we always need to consider our order of operations, otherwise known as BIDMAS. The B stands for brackets, the I for indices or powers, the D stands for division, and the M for multiplication. Finally, the A stands for addition and the S for subtraction. We work our way down from the B until we have no calculations remaining.

In this question, we have no brackets and no indices. But we have a multiplication sign and a subtraction sign. As multiplication comes before subtraction, we will multiply the two numbers either side of this sign, in this case 1.4 and three. We could work this out using standard column multiplication. Three multiplied by four is equal to 12. We put a two in the tenths column and carry the one. The decimal point must remain in the same place. Three multiplied by one is equal to three. Adding the one that we carried gives us four. Therefore, 1.4 multiplied by three is equal to 4.2.

An alternative way of performing this calculation would be to multiply one by three and 0.4 by three. One multiplied by three is equal to three and 0.4 multiplied by three is equal to 1.2. Once again, adding these numbers gives us 4.2. Our calculation, therefore, becomes 4.2 minus 2.4. We could once again work out this calculation using the column method. We cannot subtract four from two without getting a negative number. So we need to go next door to the units column and borrow one. In the tenths column, we are left with 12 minus four. This is equal to eight. Once again, we need to keep the decimal point in line. Three minus two is equal to one. Therefore, our answer is 1.8.

An alternative method to solve a calculation 4.2 minus 2.4 would be to count up using a number line. We want to find the difference between 2.4 and 4.2 or to count up from 2.4 to 4.2. The difference between 2.4 and three is 0.6. To get from three to four, we need to add one. Finally, the difference from four to 4.2 is 0.2. We need to add 0.6, one, and 0.2. This gives us an answer of 1.8. Therefore, the difference between 4.2 and 2.4 is 1.8.

The calculation 1.4 multiplied by three minus 2.4 gives us an answer of 1.8.

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