1. a is directly proportional to b. It can also be "a varies directly as b".
2. The voltage in a circuit varies jointly as the current and resistance
3. C varies jointly as a and r.
4. P and v varies jointly as t.
5. The volume of the cuboid varies jointly and inversely as the length, width, and height of the cuboid.
6. The quotient of the amount of interest and the principal amount is varies jointly as the interest rate and time. I'm not sure about this, but it could also be "the amount of interest varies directly to the principal amount and jointly to the interest rate and time".
7. The area of the rhombus varies jointly as the length of the first diagonal and the length of the second diagonal.
8. There ain't any k, but it is most likely to be this. The first area varies jointly as the second area, first base and height, and jointly and inversely as the first base and second height. Pwede rin "A1 varies jointly as A2b1h1, and jointly and inversely as b1h2.
9. The first voltage in a circuit varies directly as the second voltage, and varies jointly as the first current and resistance, and varies jointly and inversely as the second current and resistance.
10. The area of a triangle varies jointly as the base and height.
Answers & Comments
1. a is directly proportional to b. It can also be "a varies directly as b".
2. The voltage in a circuit varies jointly as the current and resistance
3. C varies jointly as a and r.
4. P and v varies jointly as t.
5. The volume of the cuboid varies jointly and inversely as the length, width, and height of the cuboid.
6. The quotient of the amount of interest and the principal amount is varies jointly as the interest rate and time. I'm not sure about this, but it could also be "the amount of interest varies directly to the principal amount and jointly to the interest rate and time".
7. The area of the rhombus varies jointly as the length of the first diagonal and the length of the second diagonal.
8. There ain't any k, but it is most likely to be this. The first area varies jointly as the second area, first base and height, and jointly and inversely as the first base and second height. Pwede rin "A1 varies jointly as A2b1h1, and jointly and inversely as b1h2.
9. The first voltage in a circuit varies directly as the second voltage, and varies jointly as the first current and resistance, and varies jointly and inversely as the second current and resistance.
10. The area of a triangle varies jointly as the base and height.