Question

A boy spends rs.10 on first day, rs.20 on second day, rs.40 on third day and so on. Find how much, in all, will he spend in 12 days ?

Answer 1

The given pattern is in gp

Gp stands for geoetric progression

So a=10

And common ratio r = 2 as the money spent gets doubled after each day

So 

Term 12 or 12th term = ar^n-1= ar^11 = 10 × 2^11=10 × 2048 = 20480


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Plz mark brainliest Alternative way- 1. 10 2. 20 3. 40 4.80 5.160 6. 320 7. 640 8. 1280 9. 2560 10. 5120 11. 10240 12. 20480 Okay so the question says in all Therefore 20480+10240+5120+2560+1280+640+320+160+80+40+20+10
30720+7680+1920+480+120+30
38400+2400+150
40800+150
40950

Answer 2

Concept Introduction:

A sort of sequence known as geometric progression (GP) is one in which each following phrase is created by multiplying each preceding term by a set number, or "common ratio." This progression is sometimes referred to as a pattern-following geometric sequence of integers.

Given: A boy spends Rs.$10$ on first day, Rs.$20$ on second day, Rs.$40$ on third day and so on.

To Find:

We have to find the value of, amount of money spent in $12$ days.

Solution:

According to the problem,

$Sn=\frac{a{(r^{n}-1}) }{r-1}$

$=\frac{10*(2^{12} -1)}{2-1} =10(4096-1)=10*4095=40950$ Rs.

Final Answer:

The value of amount of money spent in $12$ days is Rs. $40950$.

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