MP3 player

Mary plans to buy a new MP3 player for 90 USD. And every month, the amount he saved in the previous month doubles. If she saves 3 USD in the first month, how many months will Mary save enough to buy an MP3 player?

Correct answer:

n =  5

Step-by-step explanation:

a1=3 USD q=2 s=90 USD  s = a1   q1qn1  qn = 1 + a1s (q1)  k=1+a1s (q1)=1+390 (21)=31   qn=k  n ln q = ln k  n1=lnk/lnq=ln31/ln24.9542  n=[n1]=[4.9542]=5



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Showing 2 comments:
Math student
(4 × 5) + (4 × 6) + (4 × 6) + 1/2 (4 × 6) + 1/2 (4 × 6)

Math student
What's 7/10





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