Ratio, Proportion
- If p : q : r = 1 : 2 : 4, then √ 5p2 + q2 + r2 is equal to
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p = q = r = k (let) 1 2 4
⇒ p = k, q = 2k, r = 4k
∴ √ 5p2 + q2 + r2
√ 5k2 + 4k2 + 16k2 = √ 25k2
= 5k = 5pCorrect Option: C
p = q = r = k (let) 1 2 4
⇒ p = k, q = 2k, r = 4k
∴ √ 5p2 + q2 + r2
√ 5k2 + 4k2 + 16k2 = √ 25k2
= 5k = 5p
- The mean proportional between (3 + √2) and (12 − √32) is
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Mean proportional
√(3 + √2)(12 − √32)
√(3 + √2)4 (3 − √2)
= 2√9 − 2
= 2√7Correct Option: B
Mean proportional
√(3 + √2)(12 − √32)
√(3 + √2)4 (3 − √2)
= 2√9 − 2
= 2√7
- If x : y = 2 : 3, then the value of
3x + 2y is equal to 9x + 5y
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Given, x = 2 ..... (i) y 3 Expression = 3x + 2y 9x + 5y = 3 × 2 + 2 [from (i)] 3 9 × 2 + 5 3 = 2 + 2 = 4 11 11 Correct Option: B
Given, x = 2 ..... (i) y 3 Expression = 3x + 2y 9x + 5y = 3 × 2 + 2 [from (i)] 3 9 × 2 + 5 3 = 2 + 2 = 4 11 11
- If x : y = 2 : 3, then the value of
3x + 2y is equal to 9x + 5y
-
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Given, x = 2 ..... (i) y 3 Expression = 3x + 2y 9x + 5y = 3 × 2 + 2 [from (i)] 3 9 × 2 + 5 3 = 2 + 2 = 4 11 11 Correct Option: B
Given, x = 2 ..... (i) y 3 Expression = 3x + 2y 9x + 5y = 3 × 2 + 2 [from (i)] 3 9 × 2 + 5 3 = 2 + 2 = 4 11 11
- If a, b, c are three numbers such that a : b = 3 : 4 and b : c = 8 : 9, then a : c is equal to
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We can write a : c by compounding a : b and b : c
a = a × b , a = 3 × 8 , a = 2 c b c c 4 9 c 3
⇒ a : c = 2 : 3
Second Method :
A : C = xp : yq
= 3 × 8 : 4 × 9 = 2 : 3Correct Option: B
We can write a : c by compounding a : b and b : c
a = a × b , a = 3 × 8 , a = 2 c b c c 4 9 c 3
⇒ a : c = 2 : 3
Second Method :
A : C = xp : yq
= 3 × 8 : 4 × 9 = 2 : 3