Question:
How many multiples of 4 lie between 10 and 250?
Solution:
In this problem, we need to find out how many multiples of 4 lie between 10 and 250.
So, we know that the first multiple of 4 after 10 is 12 and the last multiple of 4 before 250 is 248. Also, all the terms which are divisible by 4 will form an A.P. with the common difference of 4.
So here,
First term (a) = 12
Last term (an) = 248
Common difference (d) = 4
So, let us take the number of terms as n
Now, as we know,
$a_{n}=a+(n-1) d$
So, for the last term,
$248=12+(n-1) 4$
$248=12+4 n-4$
$248=8+4 n$
$248-8=4 n$
Further simplifying,
$240=4 n$
$n=\frac{240}{4}$
$n=60$
Therefore, the number of multiples of 4 that lie between 10 and 250 is 60 .