Question

if 21y 5 id a multiple of a 9, where y ia a digit, what is the value of y?​

Answer 1

Answer:

if 21y5 is a multiple of 9 and y is a digit,then the sum of all the digits must be multiple of 9 and the unit digit sum must be 9, therefore 2+1+y+5=8+y which is equal to 9,then y =1.