Question : To do a certain task X would take 3 times as long as Y and Z together, and Z would take 4 times as long as Y and X together. Three of them together can complete the task in 10 days. How much time is taken by X and Z to complete the task?
Option 1: $18 \frac{2}{9}$ days
Option 2: $20 \frac{1}{9}$ days
Option 3: $21 \frac{1}{9}$ days
Option 4: $22 \frac{2}{9}$ days
Correct Answer: $22 \frac{2}{9}$ days
Solution : Given, To do a certain task, X takes 3 times as long as Y and Z together, Z takes 4 times as long as Y and X together, Three of them together can complete the task in 10 days. We know, Total work = Time × Efficiency Let the efficiency of X, Y, and Z be a, b, and c respectively and total work be W According to the question, W = 10(a + b + c) ....................(1) X takes 3 times (Y + Z) ⇒ (b + c) = 3a Putting this in (1) ⇒ W = 10(a + 3a) ⇒ W = 10(4a) ⇒ W = 40a ⇒ a = $\frac{\text{W}}{40}$ Z takes 4 times (X + Y) ⇒ (a + b) = 4c Putting this in (1) ⇒ W = 10(4c + c) ⇒ W = 10(5c) ⇒ W = 50c ⇒ c = $\frac{\text{W}}{50}$ Now X and Z are working together and considering total work as 1 then, ⇒ X + Z = a + c ⇒ X + Z = $\frac{1}{40} + \frac{1}{50}$ ⇒ X + Z = $\frac{5 + 4}{200}$ ⇒ X + Z = $\frac{9}{200}$ ⇒ Time taken by X and Z to complete a task = $\frac{200}{9}$ days = $22\frac29$ days Hence, the correct answer is $22\frac29$ days.
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Question : What is $\frac{\left (x^{2}-y^{2} \right)^{3}+\left (y^{2}-z^{2} \right )^{3}+\left (z^{2}-x^{2} \right )^{3}}{\left (x-y \right)^{3}+\left (y-z \right )^{3}+\left (z-x \right)^{3}}?$
Option 1: $\frac{(x+y)(y+z)}{(x+z)}$
Option 2: $(x+y)^3(y+z)^3(z+x)^3$
Option 3: $(x+y)(y+z)(z+x)$
Option 4: $(x+y)(y+z)$
Question : If $x^2 = y+z$, $y^2=z+x$, $z^2=x+y$, then the value of $\frac{1}{x+1}+\frac{1}{y+1}+\frac{1}{z+1}$ is:
Option 1: –1
Option 2: 1
Option 3: 2
Option 4: 4
Question : The value of $\frac{(x-y)^3+(y-z)^3+(z-x)^3}{\left(x^2-y^2\right)^3+\left(y^2-z^2\right)^3+\left(z^2-x^2\right)^3}$, where $x \neq y \neq z$, is:
Option 1: $0$
Option 2: $\frac{1}{(x+y+z)}$
Option 3: $\frac{1}{(x+y)(y+z)(z+x)}$
Option 4: $1$
Question : If $\frac{1}{x+2}=\frac{3}{y+3}=\frac{1331}{z+1331}=\frac{1}{3}$, then what is the value of $\frac{x}{x+1}+\frac{y}{y+6}+\frac{z}{z+2662}$?
Option 2: $1$
Option 3: $\frac{3}{2}$
Option 4: $3$
Question : If $x+y=2z$, then the value of $\frac{x}{x-z}+\frac{z}{y-z}$ is:
Option 1: $1$
Option 2: $3$
Option 3: $\frac{1}{2}$
Option 4: $2$
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