Delhi Police Constable Exam Model Paper 3

GIVEN:
Numbers between 31 and 491
FORMULA USED:
Nthterm=Tn=a+(n–1)d
CALCULATION:
Numbers which are divisible by both 3 and 5 = Numbers which are divisible by 15.
Numbers between 31 and 491 which are divisible by 15 = 45, 60, 75, 90, …………., 480
Let ‘n’ numbers are divisible by 15.
Now, 480=45+(n–1)×15
⇒ 15(n–1)=435
⇒ (n–1)=29
⇒ n=30
Hence, total numbers = 30