Question 83

How many integers are there from 200 to 400 which are multiples of 7?

Solution

The numbers which are divisible by 7, in between 200 to 400 are given below,

$$203,210, 217..........399$$

We know for the AP series,

$$\Rightarrow t_n=a+(n-1)d$$

$$\Rightarrow 399=203+7(n-1)$$

$$\Rightarrow 7(n-1)=399-203=196$$

$$\Rightarrow n-1=\dfrac{196}{7}$$

$$n=28+1=29$$

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