Number Play Class 8 Short Question Answer

Number Play Class 8 Short Question Answer

Number Play Class 8 Short Question Answer

Question 1.

If a 4-digit number 20x3 is divisible by 3, then find the values of x.

Solution:

Sum of the digits = 2 + 0 + x + 3 = 5 + x. For divisibility by 3, x = 1 or 4 or 7 (because 6, 9 and 12 are divisible by 3).

Hence, the required values of x can be 1 or 4 or 7.

Question 2.

A seven digit number 31y4673 is divisible by 9. Find the value of y.

Solution:

Sum of the digits = 3 + 1 + y + 4 + 6 + 7 + 3 = 24 + y.

For divisibility by 9,24 + y must be divisible by 9.

So, required value of y is 3 (because 24 + 3 = 27).

Question 3.

Find the values of A and B in the following:

Solution:

Clearly, the product is of the form 111, 222, 333, etc.

111 and 333 is not divisible by 6. We take 222 ÷ 6 = 37. So, we reject 222 because unit digit of 37 is not 2. Now, we take 444 and divide it by 6. We get 444 ÷ 6 = 74. Here, unit digit of 74 is 4. So, we have

Thus, A = 7 and B = 4.

Question 4.

Find whether the number 81873 is divisible by 11 or not.

Solution:

Sum of the alternate digits are 8 + 8 + 3 = 19 and 1 + 7 = 8.

The difference 19 - 8 = 11 is divisible by 11. So, the number 81873 is divisible by 11.

Question 5.

Find the parity of the digital root of the number 981704.

Solution:

Sum of digits = 9 + 8 + 1 + 7 + 0 + 4 = 29.

Again, sum of the digits = 2 + 9 = 11.

Again, sum of the digits = 1 + 1 = 2.

So, digital root is 2 and its parity is even.