Find the sum of all natural numbers between a and 100, which are divis

1.	Find the sum of all natural numbers between a and 100, which are divisible by 3.
Answer» a = 3, l = 99, n = 33 S₃₃ = \(\frac{33}{2} (a + l)\) = \(\frac{33}{2} (3 + 99)\) = \(\frac{33}{2}\) (3 + 99) = \(\frac{33}{2}\) (102) = 33 (51) = 1683

Find the sum of all natural numbers between a and 100, which are divisible by 3.

Answer»

a = 3,

l = 99,

n = 33

S₃₃ = \(\frac{33}{2} (a + l)\)

= \(\frac{33}{2} (3 + 99)\)

= \(\frac{33}{2}\) (3 + 99)

= \(\frac{33}{2}\) (102)

= 33 (51) = 1683