Question

helo friends plz help me. it is maths​

Answer 1

Questions are in sum of A.P.

so u can use A.P. sum formula to calculate them,

Sum of A.P. {S(n)} = no.of terms(n) /2{2 x first term(a)+ (n- 1) x common difference (d) }

i.e. S(n) = n/2{ 2a + (n-1)d }

and if last term is given then u will use,

S(n) = n/2 (a + last term). like in question no.3 , 5 ,6, 7 ,9

Question 1 .

Given : a = 3 , d = 5 - 3 = 2 and n = 20 so , put it in formula

S(n) = 20/2 {2 x 3 + (20-1) 2 }

S(n) = 10 x {6 + 38}

S(n) = 10 x 44

S(n) = 440

I hope it will help u to find solutions of other questions...