| 21 | .651 | |
| .07295 | ||
| 21 | .57805 | Ans. |
Write the first number under the second, so that the point comes under the point. Remember that we may consider there are 0’s above the 9 and 5, since in 21.651 there are no ten-thousandths and no hundred-thousandths.
Say, mentally 5 and 5 make 10, carry 1.
Say, mentally 10 and 0 make 10, carry 1.
Say, mentally 3 and 8 make 11, carry 1, etc.
Multiplication in Decimals
Rule.—Multiply as in whole numbers, and point off from the right of the product as many places as there are decimal places in both multiplier and multiplicand—prefixing ciphers if necessary.
Example 1: Multiply 87.432 by 564.
| 87 | .432 | |
| 564 | ||
| 43716 | .0 | |
| 5245 | .92 | |
| 349 | .728 | |
| 49311 | .648 | Ans. |
Place the multiplier so that its unit’s digit comes under the right-hand digit of the multiplicand. Then place the first figure of each product underneath the multiplying digit. The decimal point of the answer will then be directly under the decimal point of the multiplicand.