In the above problem, you want to find the number of multiples of 7 between 30 and 300.
This is an Arithmetic progression where you have n number of terms between 30 and 300 that are multiples of 7. So it is evident that the common difference here is 7.
Arithmetic progression is a sequence of numbers where each new number in the sequence is generated by adding a constant value (in the above case, it is 7) to the preceding number, called the common difference (d)
In the above case, the first number after 30 that is a multiple of 7 is 35
So first number (a) = 35
The last number in the sequence less than 300 that is a multiple of 7 is 294
So, last number (l) = 294
Common difference (d) = 7
The formula to find the number of terms in the sequence (n) is,
n = ((l - a) ÷ d) + 1 = ((294 - 35) ÷ 7) + 1 = (259 ÷ 7) + 1 = 37 + 1 = 38