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Question

If

p ∶ q = 1 ∶ 2

q ∶ r = 4 ∶ 3

r ∶ s = 4 ∶ 5

and u is 50% more than s, what is the ratio p ∶ u? 

The correct answer is

16 ∶ 45

Ratio Problem Introduction

This problem involves understanding and combining multiple ratios to find a final desired ratio. We are given several relationships between variables p$, q$, r$, s$, and u$.

Our goal is to determine the ratio of p$ to u$, which is expressed as pu$.

Given Ratio Information

Let's list down all the given ratios and the additional relationship for variable u$:

  • The ratio of p$ to q$ is 12$. This can be written mathematically as p/q=1/2$.
  • The ratio of q$ to r$ is 43$. This means q/r=4/3$.
  • The ratio of r$ to s$ is 45$. This means r/s=4/5$.
  • The variable u$ is 50%$ more than s$. This can be translated into the equation u=s+0.50s=1.5s$, or equivalently, as a fraction, u=32s$.

Combining Ratios: Step-by-Step

To find the ratio pu$, our first essential step is to combine the individual ratios into a single continuous ratio for pqrs$.

Step 1: Combine pq$ and qr$

We are given the following ratios:

  • pq=12$
  • qr=43$

To combine these ratios, the value representing q$ must be consistent. In the first ratio, q$ is 2$, and in the second, it is 4$. The Least Common Multiple (LCM) of 2$ and 4$ is 4$.

To make the q$ value 4$ in the first ratio, we multiply both parts of pq$ by 2$:

pq=(1×2)(2×2)=24$

Now that the q$ values are consistent, we can write the combined ratio:

pqr=243$

Step 2: Combine pqr$ and rs$

We now have:

  • pqr=243$
  • rs=45$

The common variable here is r$. The values for r$ are 3$ and 4$. The LCM of 3$ and 4$ is 12$.

To make the r$ value 12$ in the first combined ratio pqr$, we multiply all parts by 4$:

pqr=(2×4)(4×4)(3×4)=81612$

To make the r$ value 12$ in the ratio rs$, we multiply both parts by 3$:

rs=(4×3)(5×3)=1215$

Now that all common terms are consistent, we can combine all four variables into a single continuous ratio:

pqrs=8161215$

Ratios to Combine Common Term LCM of Common Terms Adjusted Ratios and Combined Result
pq=12$
qr=43$
q$ 4$ pq=(1×2)(2×2)=24$
qr=43$
&impliespqr=243$
pqr=243$
rs=45$
r$ 12$ pqr=(2×4)(4×4)(3×4)=81612$
rs=(4×3)(5×3)=1215$
&impliespqrs=8161215$

Calculating the Ratio p ∶ u

From our combined ratio pqrs=8161215$, we can express p$ and s$ in terms of a common constant k$. Let p=8k$ and s=15k$.

We are also given that u$ is 50%$ more than s$. This means:

u=s+50%ofs$

u=s+50100s$

u=s+12s$

u=32s$

Now, substitute the value of s$ from the combined ratio into the equation for u$:

u=32(15k)$

u=452k$

Finally, we can determine the ratio pu$:

pu=8k452k$

We can divide both sides of the ratio by k$ (assuming k$ is not zero):

pu=8452$

To eliminate the fraction in the ratio, multiply both sides of the ratio by 2$:

pu=(8×2)(452×2)$

pu=1645$

Final Answer

The final ratio of p$ to u$ is 1645$.

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Important Questions from Ratio and Proportion

  1. In a mixture of 156 litres, the ratio of milk and water is 7 : 6. How much water should be added to make the ratio 14 : 13?

  2. If the ratio of the first to second number is 3 : 4 and that of the second to the third number is 8 : 5, and sum of three numbers is 190 then the third number is:

  3. The third proportional to 9 and 15 is:

  4. The average age of 3 persons is 30 years.If their ages are in the ratio of 3 : 5 : 7 respectively, then the age of the eldest person is:

  5. The income of A and B are in the ratio 5 : 3. The expenses of A, B and C are in the ratio of 8 : 5 : 2. If C spends 2000 and B saves ₹ 700, then A saves:

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