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If 7, 11, 21 and k are in proportion, the value of k is:
45
42
33
28
33
For four numbers a, b, c, and d to be in proportion, the product of the means equals the product of the extremes: a ├Ч d = b ├Ч c. So, 7 ├Ч k = 11 ├Ч 21.
Four numbers 7, 11, 21, and k are in proportion.
baтАЛ=dcтАЛ
For four numbers a, b, c, and d to be in proportion, the product of the means equals the product of the extremes: a ├Ч d = b ├Ч c. So, 7 ├Ч k = 11 ├Ч 21.
Confusing the order of terms. Ensure you set the proportion as (first/second) = (third/fourth), which is 7/11 = 21/k.
Define the Proportion
If four numbers a, b, c, and d are in proportion, they satisfy the ratio equation baтАЛ=dcтАЛ.
117тАЛ=k21тАЛ
Cross-Multiply
Apply the cross-multiplication rule to solve for the unknown variable k.
7├Чk=11├Ч21
Solve for k
Divide both sides by 7 to isolate k. Note that 21 divided by 7 equals 3.
k=711├Ч21тАЛ=11├Ч3=33
C is correct because the calculation 711├Ч21тАЛ yields 33.
This concept is fundamental for ratio and proportion problems in Quantitative Aptitude and serves as a building block for direct and inverse variation problems in physics.
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