Question

T minutes ,N people with the formula = t= 5n^2 +15
a)When there is four people what's the minutes
b) when the time is 2hours 20mins how many people

Answer 1

Answer:

a) n = 4 , t = ?

$t = 5 {n}^{2} + 15 \\ \\ t = 5 {(4)}^{2} + 15 \\ \\ t = 5(16) + 15 \\ \\ t = 80 + 15 \\ \\ t = 95 \: min$

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b) n = ? ,

t = 2hours 20mins ––> t = (2× 60) mins + 20 mins

t = 120 + 20 = 140 mins

so; time in the mins = 140 mins

$t = 5 {n}^{2} + 15 \\ \\ 140 = 5 {n}^{2} + 15 \\ \\ 5 {n}^{2} = 140 - 15 \\ \\ 5 {n}^{2} = 125 \\ \\ {n}^{2} = \frac{125}{5} \\ \\ {n}^{2} = 25 \\ \\ n = 5$

so ; five people in 2hours 20mins