The Student Room Group

Simple geometric progression question

Part b...

why is it 1 - 0.86^7
Reply 1
Original post by IShouldBeRevising_
Part b...

why is it 1 - 0.86^7


Did you forget to attach something?
Original post by BabyMaths
Did you forget to attach something?


It's not the first time ...

Reply 3
P(T<8)=P(T=1)+P(T=2).....P(T=6)+P(T=7)

=0.14+0.14x0.86+0.14x0.86^2......0.14x0.86^6

=0.14(10.86710.86=\frac{0.14(1-0.86^7}{1-0.86}

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