Answer:
Start with 30 assembled, parts for 100 more.
Each minute results in +1/8 and -1/10
So we want
30 + x/8 - x/10 = 35
x/8 - x/10 = 5
5x - 4x = 200
x = 200 minutes
During 200 minutes, 25 are assembled, 20 are disassembled,
resulting in a net gain of 5, added to the original 30.
Bike ride:
Total distance: 40 km
Desired average speed 20 km/hr
Total time will be 2 hours
20 km at 15 km / hr = 4/3 hour taken
Leaves 2/3 hour for 20 km
20 km in 2/3 hour = 30 km/hr
Gas mileage:
Let m = city mileage
m + 3 = highway mileage
136 / (m+3) + 155 / m = 9
9m^2 - 264m - 465 = 0
m = 31 (discarding negative value)
Bricklaying:
Let b = number of bricks in wall
Lisa lays b/9 bricks per hour
Lauren lays b/10 bricks per hour
b = 5 * (b/9 + b/10 - 10)
b = 5b/9 + 5b/10 - 50
90b = 50b + 45b - 4500
b = 900
Lisa does 100 per hour
Lauren does 90 per hour
Together they do 180 per hour.
That's enough work for one Yahoo Question
The tugboat problem, in various forms I have answered before -
it has appeared many times on Yahoo Answers, sometimes with ferry boats,
sometimes with sailboats.
The ant path problem also can be found on the web in many places I am sure.
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gassaway's avatar
gassaway
Lv 4
4 years ago
three. 80x four. 80x + a million five. 250(80x + a million) 6. 250(80x + a million) + y 7. 250(80x + a million) + 2y eight. 250(80x + a million) + 2y - 250 nine. [250(80x + a million) + 2y - 250] / two = [20000x + 250 + 2y - 250] / two = [20000x + 2y] / two = 10000x + y
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