Problem Solving

What is the number of three-digit multiples of 5 that are not divisible by 10?
a) 90
b) 100
c) 180
d) 200
e) 1000

Anaira Mitch wrote:What is the number of three-digit multiples of 5 that are not divisible by 10?
a) 90
b) 100
c) 180
d) 200
e) 1000

Number of options for the hundreds digit = 9. (Any digit 1-9.)
Number of options for the tens digit = 10. (Any digit 0-9.)
Number of options for the units digit = 1. (Must be 5.)
To combine these options, we multiply:
9*10*1 = 90.

The correct answer is A.

Hello Anaira.

You have to build the three-digit number. We have 3 places _ _ _.

_ For the first place you can select any number form 1 to 9. (9 options)

_ _ For the second place you can select any number from 0 to 9. (10 options).

_ _ _ For the last option you can select only the number 5. (1 option). Why? Because you want the number will be multiple of 5 but not of 10.

So, the total of numbers that satisfy the condition is the prodcut of the options for each place, that is to say, 9*10*1=90.

So, the correct answer is A.

I really hope this question can help you.

Regards.