Question

4. If 21y5 is a multiple of 9 ,where y is a digit , what is the value of y...​

Answer 1

Answer:

21y5 is a number.

Y is a digit.

21y5 is completely divisible by 9.

The divisibility test of 9 states that the sum of digits of the number should be completely divisible by 9.

TO FIND THE VALUE OF Y:

Step 1:- Look at the constant digits i.e. the numbers whose values are fixed and known to us. In this case the constants are 2, 1 and 5.

Step 2:- Now we will add the constants. (2+1+5= 8)

Step 3:- Now that we know the sum of the constants(which is 8 in this case), we will search for the next multiple of 9. For example- In your case, the sum of known digits is 8. The multiple of nine that comes after 8 is 9 itself. So, this means that the sum of digits of the number should be 9. Remember, that in this step, you always have to search for the next multiple of 9. (10, next 18. 21, next 27 etc.)

Step 4:- 2+1+y+5= 9

8+y= 9

Y= 9-8

Y= 1

In the case of this number, the value of y= 1.

Hope it helps you.

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