Answer:
50 minutes
Step-by-step explanation:
To answer this question we should understand the fact that speed is inversely proportional to time taken to travel a distance
The higher the speed the less the time taken
We also have the relationship
Speed = Distance/Time
or
Distance/Time = Speed
We are not given the distance that Thando travelled. Let us call it D
For the first case at 100 km/hr he takes 40 minutes. We therefore have our first equation
(1) D/40 = 100
Our second equation at a speed of 80 km/hour is
(2) D/T = 80 where T is the time taken to travel distance D
Divide Equation (1) by Equation (2) to get
[tex]\dfrac{D/40}{D/T} = \dfrac{100}{80}\\\\\\\dfrac{D/40}{D/T} = D/40 \times T/D = \dfrac{T}{40}[/tex]
(When the divisor is a fraction, flip the fraction and multiply)
Therefore we get the resultant equation
[tex]\dfrac{T}{40} = \dfrac{100}{80}\\\\\text{Multiply both sides by 40 to isolate T on the left side}\\\dfrac{T}{40} \times 40 = \dfrac{100}{80} \times 40\\\\\\T = \dfrac{100}{2}\\\\= 50 \text { minutes}[/tex]
