Question

4. The following numbers are divisible by 15. Give
the possible values of a, b , c in the numbers
(1) 24b5 (2 ) 9a80 (3 ) 78b5
Please explain step by step ​

Answer 1

if any number is divided by 3 and 5 then the number is also divisible by 15

now, the divisibility rule of 3 is if the sum of all the digits are divisibel by 3 then the number is also divisible by 3

the divisibility rule of 5 is if the last digit is 0 or 5

in1)the sum of all digit=(2+4+5+b)

=11+b

therefore, the nearest number to 11 divisible by 3 is 12

therefore, b=12-11

=1

since, the last digit is 5 theregore it the number is also divisible by 5

2)sum of digit=(9+a+8+0)=17+a

therefore a=18-17=1

since , the last digit is 0 then it is divisible by 5

3)sum of digit=(7+8+5+b)=20+b

therefore, b=21-20=1

since, the last digit is 5

therefore, the number is divisible by 5