# Math Help - inverse and direct variation

1. ## inverse and direct variation

1. If d varies directly as t, and if d=4 when t=9, find d when t=21
2. If v is directly proportional to w, and if v=-6 when w=15, find w when v=3
3. If x is directly proportional to y, and if x=a when y=b, find x when y=3b
4. If a varies directly as b, and if a=5 when b=6, find a when b-1=11
5. A fish with a mass of 3kg causes a fishing pole to bend 9 cm. If the amount of bending varies directly as the mass, how much will the pole bend for a 2 kg fish?
6. The mass of a uniform copper bar varies directly as its length. If a bar 40 cm long has a mass of approximately 420 g, find the mass of a bar 136 cm long.
7. A tropical fern 90 cm tall has fronds that are 3 cm long. A fossil of the same kind of fern was found if the height of this type of fern varies directly as the length of its fronds, what must the height of the fossilized fern have been if one of its fronds was 4.8 cm. long?
8. The 220 km bus trip to the math league competition cost each of the students from canton $26.40. Using the same bus company, the students from Hampton paid$42 each. If the bus fare is directly proportional to the number of kilometers traveled, how far was the Hampton Students' trip?

Well im not a fan of getting homework off people but I have to go to sleep because it took me a while to study my english vocab words please answer all and maybe if you have time for this poor kid leave commentary on how it is done top right it says Y=kx $n$

THANXZ TO U ALLZ

2. Originally Posted by HamzaH
1. If d varies directly as t, and if d=4 when t=9, find d when t=21
2. If v is directly proportional to w, and if v=-6 when w=15, find w when v=3
3. If x is directly proportional to y, and if x=a when y=b, find x when y=3b
4. If a varies directly as b, and if a=5 when b=6, find a when b-1=11
5. A fish with a mass of 3kg causes a fishing pole to bend 9 cm. If the amount of bending varies directly as the mass, how much will the pole bend for a 2 kg fish?
6. The mass of a uniform copper bar varies directly as its length. If a bar 40 cm long has a mass of approximately 420 g, find the mass of a bar 136 cm long.
7. A tropical fern 90 cm tall has fronds that are 3 cm long. A fossil of the same kind of fern was found if the height of this type of fern varies directly as the length of its fronds, what must the height of the fossilized fern have been if one of its fronds was 4.8 cm. long?
8. The 220 km bus trip to the math league competition cost each of the students from canton $26.40. Using the same bus company, the students from Hampton paid$42 each. If the bus fare is directly proportional to the number of kilometers traveled, how far was the Hampton Students' trip?

Well im not a fan of getting homework off people but I have to go to sleep because it took me a while to study my english vocab words please answer all and maybe if you have time for this poor kid leave commentary on how it is done top right it says Y=kx $n$

THANXZ TO U ALLZ
1. $d \propto t \Rightarrow d = kt$.
Substitute d=4 when t=9 to solve for k: $4 = 9k \Rightarrow k = \frac{4}{9}$.
Therefore $d = \frac{4t}{9}$.
Now get d when t = 21: $d = \frac{(4)(21)}{9} = \, ....$