What is the sum of first five multiples of 3?

The first five multiples of 3 are 3, 6, 9, 12, 15
It is in the form of A.P
Here, 𝑛 = 5, 𝑎 = 3 𝑎𝑛𝑑 𝑙 = 15
⇒ 𝑆 =𝑛/2(𝑎 + 𝑙)
⇒ 𝑆 =5/2(3 + 15)
⇒ 𝑆 =5/2(18)
⇒ 𝑆 = 45 

The sum of first five multiples of 3 is 45 Hence option (𝑎)45 is correct.