October 6, 2020

Developing a simpler rule of divisibility for 8 to make learning easier

By: SRISTI ORG / Inshodh / 0 comment

Sursinh Parmar

The innovation sprang from the question posed by a student of standard 5, which posed a challenge to teacher to invent a new key to see whether a given number is divisible by 8. He then developed a process to ascertain whether a given number was divisible by 8; See and ensure that the last two digits of the given number are multiples of 4 (if it is not then that particular number can’t be divided by 8 without reminder); Also look at the multiplier of last two digits, whether is it even or odd; Look at the number in the hundred’s place. If the multiplier and number in the hundred’s place are both, odd or even, then the given number can be divided by 8 without a remainder. The following example will make it clear : Take a number. Here, let’s take 1, 24,336. The last two digits (36) are multiple of 4 (9*4=36). The multiplier of last two digits (9) is odd. The number in the hundred’s place (3) is also odd. So this number is divisible by 8. Following table will further explain the concept with better clarity

Number (for example)
Whether the last two digits (Ones and tens) are multiples of 4?
Which is the multiple of 4?
Whether the multiplier is odd or even
Whether the place of hundred in the number is odd or even
Whether it is divisible by 8 or not?
1,23,632
32 P
8 X 4 = 32
Even
6 – Even
YES
76,76,776
76 P
19 X 4 = 76
Odd
7 – Odd
YES
12,12,116
16 P
4 X 4 = 16
Even
1 – Odd
NO
42,42,852
52 P
 13 X 4 = 52
Odd
8 – Even
NO
42,42,200
00 P
00 X 4 = 00
Even
2 – Even
YES
45,78,423
23 X
 
 
 
NO

This kind of process, if explained properly to children, helps them to understand whether a particular number can be divided by 8 or not. It also develops interest in maths, which otherwise is considered to be a hard subject.

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