Question

1+2+3+4+5+6+7+8+9+10×5+2-8​

Answer 1

Step-by-step explanation:

1+2+3+4+5+6+7+8+9+10×5+2-8

= (1+2+3+4+5+6+7+8+9+10)×5+(2-8)

= (55*5)+(-6)

= 275-6

= 269

Answer 2

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 × 5 + 2 - 8​ = 89

Step-by-step explanation:

We have,

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 × 5 + 2 - 8​

To find, 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 × 5 + 2 - 8​ = ?

∴ 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 × 5 + 2 - 8​

The sum of 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9

= $\dfrac{9(9+1)}{2}$ = $\dfrac{9(10)}{2}$

We know that,

1 + 2 + 3 + 4 + ...... + n = $\dfrac{n(n+1)}{2}$

= 45

∴ (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9) + 10 × 5 + 2 - 8​

= 45 + 50 + 2 - 8

= 97 - 8

= 89

∴ 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 × 5 + 2 - 8​ = 89