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Can someone please help with this math question?
![Attachment image](https://s.yimg.com/tr/i/aa8776f12ac34fd6beabfb41265901f3_A.jpeg)
3 Answers
- husoskiLv 72 years agoFavorite Answer
Suppose the original trip took t hours. The distance traveled at 50 km/h was 50t km. You're told that the return trip took 15 min. (0.25 h) longer traveling at 50+6 = 56 km/h, That's a return distance of 56(6 + 0.25) km; and that this distance is 26 km longer than the original. So:
56(t + 0.25) = 50t + 23
56t + 14 = 50t + 23
6t = 23 - 14 = 9
t = 9/6 = 1.5 h
That's the original driving time. The return trip was 0.25 hr longer:
t + 0.25 = 1.75 h
That's an hour and 45 minutes, or 105 minutes if you prefer.
- Daniel HLv 52 years ago
Distance:
d1 is distance he drove to friend's house
d2 is distance he drove back
Speed:
v1 = speed to friend's house
v2 = speed from friend's house
Time:
t1 = d1/v1
t2 = d2/v2
Things we know:
d1 = d2 - 23km
v1 = 50km/h
v2 = 56km/h
t1 = t2 - 0.25h (15min = 0.25h)
Use this equation
v1 = d1/t1
where
d1 = d2 - 23km
t1 = t2 - 0.25km = d2/v2 - 0.25h
v1 = (d2 - 23km)/(d2/v2 - 0.25h)
Multiply by d2/v2 - 0.25h
v1/v2 *d2 - 0.25h*v1 = d2 - 23km
Plug in known values for v1 and v2
50/56 d2 - 12.5km = d2 - 23km
Multiply by 56
50d2 - 700km = 56d2 - 1288km
588km = 6d2
d2 = 98km
d1 = d2 - 23km
d1 = 98km - 23km
d1 = 75km
t1 = d1/v1
t1 = 75km/50km/h
t1 = 1.5h
- la consoleLv 72 years ago
Recall: s = d/t → where s is the speed, d is the distance, t is the time
On the way to his friend's house, Latif drives at an average speed of 50 km/h.
s₁ = d₁/t₁ → where: s₁ = 50 km/h
50 = d₁/t₁
50.t₁ = d₁
When he returns home, Latif takes a longer route that has better roads.
s₂ = d₂/t₂ → he drives an extra 23 km, so: d₂ = d₁ + 23
s₂ = (d₁ + 23)/t₂ → his average speed is 6 km/h higher, so: s₂ = s₁ + 6 = 56
56 = (d₁ + 23)/t₂ → the journey takes him an extra 15 min, i.e. 0.25 h, → t₂ = t₁ + 0.25
56 = (d₁ + 23)/(t₁ + 0.25)
56.(t₁ + 0.25) = d₁ + 23 → recall: d₁ = 50.t₁
56.(t₁ + 0.25) = 50.t₁ + 23
56.t₁ + 14 = 50.t₁ + 23
56.t₁ - 50.t₁ = 23 - 14
6.t₁ = 9
t₁ = 9/6
t₁ = 1.5 hours
t₁ = 1 h + 0.5 h
t₁ = 1 h + 30 min ← to go to his friend's house
Recall:
t₂ = t₁ + 15 min
t₂ = 1 h + 30 min + 15min
t₂ = 1 h + 45 min ← to return home