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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. The cost of a diamond is directly proportional to the square of its weight. The cost of a 14 gm diamond is Rs. 2560. This diamond got broken down into two pieces in the ratio of 5 ∶ 9. How much loss percent is incurred due to this breakage ? (Correct to two decimal places)

  2. Atul purchased Bread costing Rs.20 and gave a 100 rupee note to the shopkeeper. The shopkeeper gave the balance money in coins of denomination Rs.2, Rs.5 and Rs.10. If these coins are in the ratio 5 ∶ 4 ∶ 1, then how many Rs.5 coins did the shopkeeper give?

  3. A person divides a certain amount among his three sons in the ratio of 3 ∶ 4 ∶ 5. If he had divided this amount in the ratio of 1/3,1/4,1/5, his son, who had got the lowest share earlier, would get Rs.1,188 more. Find the amount (in Rs).

  4. In a school 3/8 of the number of students are girls and the rest are boys. One-third of the number of boys are below 10 years and 2/3 the number if girls are also below 10 years. If the number of students of age 10 or more years is 260. then the number of boys in the school is:

  5. If a : b : c = \(\frac{1}{4} : \frac{1}{3} : \frac{1}{2}, \)  then  \( \ \frac{a}{b} : \frac{b}{c} : \frac{c}{a} = ?\)

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