The cost of ten books is RS.70
then what will be the cost of 20 such books.
DIRECT AND INVERSE PROPORTION.
Answers
Step-by-step explanation:
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Step-by-step explanation:
1. If x = 20 and y = 40, then x and y are:
A. Directly proportional
B. Inversely proportional
C. Neither directly nor inversely proportional
D. Cannot be determined
Answer: A
Explanation: x = 20 and y = 40
Clearly, 40 = 2 x 20
y=2x
y∝x, where 2 is the proportionality constant.
2. If x = 15 and y = 1/30, then x and y are:
A. Directly proportional
B. Inversely proportional
C. Neither directly nor inversely proportional
D. Cannot be determined
Answer: B
Explanation: x = 15, y = 1/30
1/30 = 1/(2 × 15)
y = 1/2x
Hence, y ∝ 1/x, where 1/2 is the proportionality constant.
3. If x and y are directly proportional, then which of the following is correct?
A. x+y=constant
B. x-y=constant
C. xy=constant
D. x/y=constant
Answer: D
Explanation: x∝y
x=ky
k=x/y, where k is a constant.
4. If x and y are inversely proportional, then:
A. x+y=constant
B. x-y=constant
C. xy=constant
D. x/y=constant
Answer: C
Explanation: x∝1/y
x=k/y
xy=k
Where k is a constant.
5. If x∝y and x1=5,y1=210 and x2 = 2, then find y2?
A. 200
B. 84
C. 99
D. 70
Answer: B
Explanation: x∝y
x=ky
x/y=k
x1/y1 = x2/y2
5/210 = 2/y2
y2 = 84
6. If the weight of 12 sheets of thick paper is 40 grams, how many sheets of the same paper would weigh 2500 grams?
A. 750
B. 800
C. 850
D. 950
Answer: A
Explanation: For 12 sheets, weight of paper is 40 grams
Let number of sheets for 2500 is x.
Using direct proportion concept:
12/40 = x/2500
x=(12×2500)/40
x=750