Answer:
The distance across the lake is 3.5 km
Step-by-step explanation:
Hypotenuse is divided in equal parts. Thus both sides are divided in the same proportion.
80% × x = 32
.80x = 32
x = 32/.8
x = 40
The distance, s = 40t₁ where t₁ is the time to complete the outward journey.
The same distance = vt₂ where t₂ is the time to complete the return journey at speed v.
For the whole journey, 2s=60(t₁+t₂). Therefore s=30(t₁+t₂)=40t₁=vt₂.
30t₁+30t₂=40t₁, 10t₁=30t₂, t₁=3t₂, so s=120t₂=vt₂ and v=120kph.
