Page 159 - Start Up Mathematics_8 (Non CCE)

AT a Glance

1. If x and y are two quantities and y increases with an increase in x or y decreases with a decrease in x then
x and y are in direct variation.
x x
2. 1 = k = 2 fi x : x = y : y 2
1
1
2
y 1 y 2
3. If x and y are two quantities and y increases with a decrease in x or y decreases with an increase in x then
x and y are in inverse variation.
4. x y = k = x y 2 fi x : x = y : y 1
1 1
2
1
2
2
Review Exercises
Multiple ChoiCe Questions

1. The quantity of rice sold by two shopkeepers is in the ratio 3 : 5. If the second shopkeeper sold 25 kg of
rice, the quantity of rice sold by the first shopkeeper is:
(a) 18 kg (b) 15 kg (c) 20 kg (d) 12 kg
2. 30 men take 10 days to build a wall. 25 men will take how many days to build a wall?
(a) 13 (b) 11 (c) 12 (d) 14
3. x is in inverse variation with y. If x is 8 and the constant of variation is 48, the value of y is:
(a) 9 (b) 13 (c) 12 (d) 6
4. Pinky bought 15 chocolates for ` 240. Cost of 10 chocolates is:
(a) ` 160 (b) ` 155 (c) ` 150 (d) ` 165
5. If p = 4q, then p and q vary ______________ with each other.
(a) inversely (b) directly (c) insufficient information (d) none of these

solve Mentally

Fill in the Blanks
x
1. If two quantities x and y vary in such a manner that is ______________ and ______________, then
x and y are said to be in direct variation. y
5 7
2. =
15

3. The time of journey is in ______________ variation with the speed of car.
4. If xy = 48 and y = 6, then x = ______________.

Answer in One Word Or a Line
1. What is variation? What are the types of variation?
2. Does weight of rice (x) and its cost (y) show direct variation?
3. If 10 men can dig a pit in 14 days, in how many days can 20 men dig the pit?
4. What is the condition for two quantities to be in inverse variation?

let’s evaluate
1. A hotel paid a total of ` 5,81,760 as salaries to 24 workers in the month of March. 9 new workers joined
the hotel in April. What will be the salary bill of the hotel for April?
2. Telephone poles are fixed at an equal distance from each other. If 12 such poles are fixed over a distance
of 75 km, how many poles are required for a distance of 25 km?

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