Question

if you save rs 200 from your pocket money and in successive months twice as much as in the previous month. this process continued for seven months. From next month and onward you are able to save RS 50 less than the previous month. At the end of the year you want to purchase a laptop cost 32000 . How much more amount you need to take from your parent? Explain

Answer 1

Answer:

403661736 UID any FF players here

Answer 2

Answer:

Step-by-step explanation:

For 1st 3 months, amount = 600 Rs.

For the 4th month, amount saved is 240 Rs.

And then the saved amount increases by 40 every month

So, they form an A.P. with first term a=240 and common difference d=40

We know that, sum of n first n terms of an A.P. is

S subscript n equals n over 2 open parentheses 2 a plus left parenthesis n minus 1 right parenthesis d close parentheses

S u b t r a c t i n g space 600 space f r o m space t o t a l space a m o u n t space g i v e s space 10440 space R s.

rightwards double arrow 10440 equals n over 2 open parentheses 480 plus left parenthesis n minus 1 right parenthesis 40 close parentheses

rightwards double arrow n squared plus 11 n minus 522 equals 0

rightwards double arrow left parenthesis n plus 29 right parenthesis left parenthesis n minus 18 right parenthesis equals 0

rightwards double arrow n equals negative 29 space o r space 18

N o. space o f space m o n t h s space c a n apostrophe t space b e space n e g a t i v e comma space t h e r e f o r e space n equals 18

H e n c e comma space a space m a n space s a v e s space R s. space 11040 space a f t e r space 18 plus 3 equals 21 space m o n t h s.