Answer:
¹/₄ hr or 0.25 hrs
⁷/₆ hr or 70 mins
He will make it in time (justification below)
4.
a. False
b. True
c. False
Step-by-step explanation:
The questions are all in relation to the equation:
speed (km/hr) = distance (km)/time (hr)
It may be worth learning about how formula triangles work because I think you would find them helpful, there are videos online on this
The first question is asking about times;
Rearranging the equation/formula above, time = distance/speed;
So, we just plug in the information for each distance travelled;
The first 30 km is covered at 120 km/hr;
So, the time taken will be:
t = ³⁰/₁₂₀
This simplifies to:
t = ¹/₄ = 0.25
So, it will take ¹/₄ hr or 0.25 hrs to cover 30 km at 120 km/hr;
¹/₄ hr is the same as 15 mins
The next 56 km is covered at 48 km/hr;
So:
t = ⁵⁶/₄₈
This simplifies to:
t = ⁷/₆
So, it will take ⁷/₆ hr or 70 mins
The second question requires us to know the time taken to cover 16 km at 100 km/hr;
t = ¹⁶/₁₀₀
This simplifies to:
t = ⁴/₂₅ = 0.16
So, ⁴/₂₅ hr or 9.6 mins
If he has 15 mins to make it to school and we've just calculated it will taken 9.6 mins, then he will make it in time
4.
a.
False
Jason runs 5 km in 30 mins, which means he could run 10 km in 60 mins;
Donna runs 9 km in 60 mins, so Jason runs at a faster speed since he would cover 10 km in 60 mins
b.
True
Rachel covers 10 km in 10 mins;
Speed will be:
10/10 = 1
So, her speed is 1 km/min
An hour is 60 mins so, her speed in km/hr will be:
60 × 1 = 60
60 km/hr
This is greater than the limit 50 km/hr
c.
False
The 2 runners run the same track, this means they run the same distance;
If James takes longer, then this is because he is running slower or, in other words, Paula is running faster
d.
Can't see the full question
