Question

find a three digit number is divisible by 9 if the first digit is 7 and last is two less than 7​

Answer 1

Answer:

the answer is 736

Step-by-step explanation:

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Answer 2

Step-by-step explanation:

How many three digit numbers are divisible by 7?

Let a be the first 3-digit no. divisible by 7

To get a, divide 100 by 7. We get,

100=(7×14)+2

We know that 7×14 is a multiple of 7 and 100 is not. Since 100 is not a multiple of 7

a=100 +5 =105

[ 7×14 is 98 and next multiple of 7 is 105. 100 is only 2 times more than 98. To get the next multiple of 7 we have to add 5 to 100]

Let l be the last 3 digit no. divisible by 7

To get l we divide l by 999. We get 5 as the remainder. We subtract 5 from 999 to get l.

l= 999-5=994

We know that l=a+(n-1)d

Where, n is total no. of 3-digit numbers divisible by 7 and d is the common difference between successive numbers, which is 7

Therefore,

l=a+(n-1)d

994=105+(n-1)7

889=(n-1)7

889/7=n-1

n-1=127

n=128

Thus there are 128 3-digit numbers divisible by 7.