Question

A man receives rs.60 for first week and rs.3 more for every week than the preceding week. how much does he earn by the 20th week?

Answer 1

Answer:

He earn rs.1770 by the 20th week.

Step-by-step explanation:

We are given that A man receives rs.60 for first week and rs.3 more for every week than the preceding week.

So, First week amount = Rs 60

Since he receives rs.3 more for every week

So, Second week amount = Rs.60+Rs.3 = Rs.63

So, third week amount = Rs.63+Rs.3 = Rs.66

So, it forms AP : 60,63,66......

First term a = 60

Common difference = d = 3

So, Sum of first n terms = $S_n=\frac{n}{2}(2a+(n-1)d)$

Substitute n = 20

$S_{20}=\frac{20}{2}(2(60)+(20-1)3)$

$S_{20}=10(120+(19)3)$

$S_{20}=1770$

Hence  he earn rs.1770 by the 20th week.

Answer 2

Answer:

ans is 1770

Step-by-step explanation:

first week = 60

second week =63 { because he is getting 3 rupees every week}

so,a=60,n=20

d=63-60=3

Sn=n/2[2a(n1)d]

20/2[2(60)(20-1)3]

10[120+19*3]

10[120+57]

= 1770