Question

The time it takes to fly from Los Angeles to New York varies inversely as the speed of the plane. If the a plan flies 6 hours at 900 km/h, how long would it take at 800 km/h?

answer choices
o 5.33 hours
o 6.75 hours
o 12 hours
o 10 hours

Answer 1

it takes 6.75 hours

Explanation:

Since the time varies inversely with the speed v,we have

t ∝ 1/v

so the ratio between two values of times will be,

(t₁)/(t₂) = (1/v₁)÷(1/v₂) = (v₂)/(v₁)

(t₁)/(t₂) = (v₂)/(v₁)

in our case, it takes 6 hours at 900 km/h so t₁ = 6 h v₁ = 900 km/h

also, v₂ = 800 km/h

so we just need to find t₂,

putting values, we get,

(6/(t₂) = (800)/(900)

1/t₂ = 8/(9)(6)

1/t₂ = 4/(27)

t₂ = 27/4

t₂ = 6.75 hours