Question

(2.8 multiply 10^-3)-(0.65multiply10^-4)+(0.15multiply10^-2

Answer 1

Answer:

Step 1: Set the multiplication out as follows.

6 0 3

× 5 8

Note that the number with the smaller number of digits goes at the bottom.

Step 2: Multiply 603 by 8.

6 0 3

× 5 8

4 8 2 4

The result of 8 × 603 is shown in bold.

Step 3: Next, multiply 603 by 50. This is the same as multiplying 603 by 5 and by 10. We place a zero to the right and then write down the result of 5 × 603.

6 0 3

× 5 8

4 8 2 4

3 0 1 5 0

The result of 5 × 603 is shown in bold and the additional zero has been shown in blue.

Step 4: Finally, add these two rows together to give the final answer.

6 0 3

× 5 8

4 8 2 4

3 0 1 5 0

3 4 9 7 4

The final answer for 58 × 603 is 34974.

These techniques can be extended to numbers with any number of digits and to numbers involving decimals. For example, if the sum were 5.8 × 6.03, notice that there are 3 digits after the decimal point in total in the sum.

The answer would also have three digits after the decimal point, so instead of 34974,

5.8 × 6.03 = 34.974

Using the same rules for numbers with decimal points:

5.8 × 60.3 = 349.74

58 × 6.03 = 349.74

5.8 × 0.603 = 3.4974