Ratio and Proportion

Q 6: What must be added to each term of the ratio 2 : 3, so that it may become equal to 4 : 5? A)1 B)3 C)2 D)None of these Answer : Option C Explanation: Let the number to be added be x, then (2 + x) : (3 + x) = 4 : 5 ⇒ (2 + x)/(5 + x) = 4/5 5(2 + x) = 4(3 + x) 10 + 5x = 12 + 4x 5x - 4x = 12 - 10 x = 2 Q 7: If 10% of x = 20% of y, then x:y is equal to: A)1:1 B)3:1 C)2:2 D)2:1 Answer : Option D Explanation: 10% of x = 20% of y 10x/100 = 20y/100 => x/10 = y/5 x/y = 10/5 = 2/1 x:y = 2:1. Q 8: If x:y=5:3 then (8x-5y) : (8x+5y)=? A)6:21 B)5:11 C)2:44 D)4:11 Answer : Option B Explanation: x/y = 5/3 (8x − 5y)/(8x + 5y) =>8(x/y) − 5/8(x/y)+5 =>( on dividing Numerator and Denominator by y) =>(8(5/3) − 5)/(8(5/3) + 5) =>(40/3 − 5/1)/(40/3 + 5/1) =>[(40 − 15)/3]/[(40 + 15)/3] 25/55 = 5/11 (8x-5y):(8x+5y) = 5:11 Q 9: The proportion between the current ages of A and B is 6:7. If B is 4 years elder than A, what will be the proportion of the ages of A and B after 4 years? A)7:8 B)5:8 C)7:4 D)6:9 Answer : Option A Explanation: If A’s age and B’s age = 6a and 7a years respectively Then B is 4 years elder than A => 7a – 6a = 4 A = 4 After 4 years, A’s age = 6a + 4 years And B’s age = 7a + 4 Needed ratio = 6a + 4 : 7a + 4 Replace the “a” value of 4 = 28 : 32 =>28/32 = 7 : 8 Q 10: Right now, the proportion between the ages of Kriss and Syam is 4 : 5. After 6 years, Kriss’s age will be 26 years. As of now what is the age of Syam? A)30 Years B)21 Years C)25 Years D)None of these Answer : Option C Explanation: If the current age of Kriss = 4a and Syam =5a correspondingly. After 6 years , Kriss’s age = 4a +6 years After 6 years, Kriss’s age will be 26 years. 4a + 6 = 26 A = (26 – 6) /4 = 5 Syam’s current age is 5 x 5 = 25 years.

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