Question

the cost of digging a well after every metre digging when is cost rupees 150 for the first metre and Rises by the rupees 50 50 for each subsequent metre in answer​

Answer 1

Answer:

n/2(300+(n-1)50)

or n(125+25n)

Step-by-step explanation:

a=150 d=50 N=n

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

Sn=n/2(300+(n-1)50)

Sn=n(125+25n)

Answer 2

$\huge\fcolorbox{green}{yellow}{Answer = 50}$⠀

$\bf\huge\underline{Explanation}$

Here, the cost of digging for first 1 metre ⠀⠀= Rs 150

The cost of digging for first 2 metres ⠀⠀= Rs 150 + Rs 50 = Rs 200

The cost of digging for first 3 metres ⠀⠀= Rs 150 + (Rs 50) × 2 = Rs 250

The cost of digging for first 4 metres ⠀⠀= Rs 150 + (Rs 50) × 3 = 300

Therefore, The term are: 150, 200, 250, 300, ......

Since, 200 - 150 = 50 and 250 - 200 = 50

=> (200 - 150) = (250 - 200) = 50

Therefore, The above form an AP with common difference = 50.