- #1

- 427

- 2

## Homework Statement

How many 3 digit numbers are divisibIe by 5?

## Homework Equations

## The Attempt at a Solution

I get the answer as 136. could Someone please work it out and check my answer?

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- Thread starter Amith2006
- Start date

- #1

- 427

- 2

How many 3 digit numbers are divisibIe by 5?

I get the answer as 136. could Someone please work it out and check my answer?

- #2

- 1,753

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Attempt to a solution?

- #3

- 737

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I don't get 136. How did you come up with that answer?

- #4

Defennder

Homework Helper

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I don't get 136 either. How did you get that?

- #5

Dick

Science Advisor

Homework Helper

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- #6

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Its all the numbers that end in 5 or zero, and then ignore the last one (1000) because it had the temerity to posses 4 digits.

As you start building the sequence, you see the rule easy enough.

- #7

- 2

- 0

a_{n}=nth term of an AP (Arithmetic progression)

a=1st term

d=common difference

Since the 1st 3 digit no. divisible by 5 is 100

a=100

the last 3 digit no. divisible by 5 is 995

a_{n}=995

common difference (d)=5

n=no. of 3 digit nos. divisible by 5

a_{n}=a+(n-1)d

995=100+(n-1)5

995-100=(n-1)5

895=(n-1)5

895/5=n-1

179=n-1

179+1=n

n=180

Therefore,

exactly (not roughly) 180 3 digit numbers are divisibe by 5

Absolutely correct Dick!!!

@Amith2006

How did you get 136?!

a=1st term

d=common difference

Since the 1st 3 digit no. divisible by 5 is 100

a=100

the last 3 digit no. divisible by 5 is 995

a

common difference (d)=5

n=no. of 3 digit nos. divisible by 5

a

995=100+(n-1)5

995-100=(n-1)5

895=(n-1)5

895/5=n-1

179=n-1

179+1=n

n=180

Therefore,

exactly (not roughly) 180 3 digit numbers are divisibe by 5

Absolutely correct Dick!!!

@Amith2006

How did you get 136?!

Last edited:

- #8

Borek

Mentor

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Year that passed since the thread was started was enough to count these numbers using fingers.

- #9

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Aha that made me laugh, insane bump

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