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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. If the ratio of three numbers A, B and C is 2 ∶ 3 ∶ 5, and the sum of the squares of these numbers is 3800, then the value of C is:

  2. A bag contains ₹310 in the form of 5 rupee, 2 rupee and 1 rupee coins in the ratio 4 ∶ 3 ∶ 5. What is the number of 5 rupee coins? 

  3. The ratio of three numbers is 3 ∶ 5 ∶ 4 and the sum of their squares is 11250. Find the sum of the numbers.

  4. When 'x' is subtracted from each of the numbers 22, 39, 56 and 107, then the resulting numbers, in this order, are in proportion. What is the mean proportional between (x + 3) and (3x - 7)?

  5. The salaries of Ravi and Sumit are in the ratio 4 ∶ 5. If the salary of each is increased by Rs. 6,000 the new ratio becomes 35 ∶ 40. What will be Sumit's increased salary?

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