Question

Given that 1 + 2 + 3 + ... + 10 = 55. Then (11 +
12 + 13 + ... +20) is equal to
a. 155 b. 135 c. 165 d. 160.​

Answer 1

Answer:

(11 + 12 + 13 + ... +20) =  155

Step-by-step explanation:

Given that 1 + 2 + 3 + ... + 10 = 55

We need to find

(11 + 12 + 13 + ... +20)

Now 11 = 10 + 1

12 = 10 + 2

13 = 10 + 3

.

.

20 = 10 + 10

=> (11 + 12 + 13 + ... +20) = 10 + 1  + 10 + 2 + 10+ 3 +.............................. + 10 + 10

= 10 * 10  +  1 + 2 + 3 + ... + 10

= 100 + 55

= 155

(11 + 12 + 13 + ... +20) =  155

Answer 2

Answer:155 option a

Step-by-step explanation: