Probability question :If the probability for each canon shoots the target is 60%, which of the following of numbers of canons can reach the probability at 99%?

GRE Quant Problem Solving
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Can you guys explain the solution for this problem ?
If the probability for each canon shoots the target is 60%, which of the following of numbers of canons can reach the probability at 99%?
A) 3
B) 4
C) 5
D) 6
E) 7

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Source?

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The solution involves a logarithmic equation. Pretty sure such a question will NOT be asked. Anyway solved it till the equation.
For 1 cannon Prob= 0.6 and not hitting = 0.4
for 2 = 0.6^2
for 3 = 0.6^3
desired result: 1-0.4^n>=0.99

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adding the Screenshot for WA:

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1 Like
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Kaplan Test 7

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probability to not shoot the target = 1- 0.99 = 0.01
(1-0.6) ^ n <= 0.01
on choosing numbers, the above equation holds true at n > 5.
Isn’t it a fair question to ask by the ets too, the logic is the same. I have found a similar question in the GMAT club too