Question

10y -(2y-1)=41
Without adding find the sum : a) 1+2+3+4+5+7+9+11 b) 1+2+3+.............+21

Answer 1

Step-by-step explanation:

3.33

a) 37

b) 231

These are the answers

Hope you liked it

Answer 2

Step-by-step explanation:

10y-(2y-1)= 41

solving the bracket by multiplying the subtract sign with it

10y-2y+1 = 41

8y= 41-1= 40

y= 40/8

y= 5

2a) 42

b) can be find out by using A. P. sum formula

= Sn= n/2(2a+ (n-1) d

here a= 1 d= 1 n= 21

so Sn = 21/2(2×1+(21-1) 1

= 21/2(2+20)

21/2× 22

now 2 will cancel 22 with 11

= 21×11

= 231