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Division by 5, 50, 500 and 0.5

Last week, we discussed multiplication by 5, 50, 500 and 0.5. The short way to multiply a number by 5 is to halve it, then multiply the quotient by 10.

Now we will discuss the opposite: division by those numbers. The obvious technique is to also perform the opposite steps. To divide by 5, we can double the number then divide by ten. This topic is discussed extensively in our book, 25 Math Short Cuts which is available on MATH-Inic Philippines (https://www.facebook.com/MATHInicPhils).

We have also discussed doubling in our previous articles: https://www.math-inic.com/blog/doubling-from-left-to-right/ and https://www.math-inic.com/blog/doubling-by-number-splitting/ while dividing by 10 is done simply by moving the decimal point one place to the left.

Thus, 6420 ÷ 5 → 6420 x 2 = 12840 ÷ 10 → 1284

and   16342 ÷ 5 → 16342 x 2 = 32684 ÷ 10 → 3268.4

My personal favorite is to divide the number by 10 first then, double the result. In our 1st example 6420 ÷ 5, we can simply double 642 to get 1284 while in our 2nd example, we can think of 16, 342 as 1634.2 and double it to get 3268.4.

To divide by 50, we can divide by 100 then double: 73500 ÷ 50 = 725 x 2 = 1450 and

4326 ÷ 50 = 43.26 x 2 = 86.52.

To divide by 500, we can also double the number, then divide by 1,000: 234,000 ÷ 500 = 468,000 ÷ 1000 = 234 and 726492 ÷ 500 = 1,452,984 ÷ 1000 = 1452.984

To divide by 0.5, we simple double the number: 895 ÷ 0.5 = 1790 and 8264 ÷ 0.5 = 16,528

Try these divisions:

  1. 542 ÷ 5 =
  2. 743 ÷ 50 =
  3. 867 ÷ 500 =
  4. 927 ÷ 0.5 =
  5. 1024 ÷ 5 =
  6. 7526 ÷ 50 =
  7. 13856 ÷ 500
  8. 23254 ÷ 0.5
  9. 78946 ÷ 5000
  10. 35795 ÷ 0.05

Answers to last week’s exercise problems:

  1. 246 x 5 = 1230
  2. 3478 x 5 =17,390
  3. 156358 x 5 = 781,790
  4. 682 x 50 = 34,100
  5. 3658 x 50 = 182,900
  6. 6842 x 500 = 3,421,000
  7. 34336 x 500 = 17,168,000
  8. 2648 x 0.5 = 1324
  9. 532546 x 0.5 = 266,273
  10. 137934 x 0.5 = 68,967
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