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Question

Ananth takes 6 hours and Bharath takes 4 hours to read a book. Both started reading copies of the book at the same time. After how many hours is the number of pages remaining to be read by Ananth, twice that the number of pages remaining to read by Bharath? Assume Ananth and Bharath read all the pages with constant pace.

The correct answer is

3

Book Reading Problem: Ananth and Bharath's Pace

This problem involves understanding the concept of reading pace and calculating the number of pages remaining for two individuals, Ananth and Bharath, who read a book at different constant rates.

Reading Rates Defined

First, let's define the reading rates for both Ananth and Bharath. Let the total number of pages in the book be denoted by \(P\).

  • Ananth's time to read the entire book = 6 hours.
  • Bharath's time to read the entire book = 4 hours.

From this, we can determine their respective reading rates (pages per hour):

Reader Time to Read (Hours) Reading Rate (Pages/Hour)
Ananth 6 \(P/6\)
Bharath 4 \(P/4\)

Pages Remaining Formula

Let \(t\) be the number of hours after which we want to find the relationship between the pages remaining for Ananth and Bharath.

After \(t\) hours:

  • Pages read by Ananth = Ananth's reading rate \(\times\) time = \(\left(\frac{P}{6}\right) \times t = \frac{Pt}{6}\).
  • Pages remaining for Ananth (\(R_A\)) = Total pages - Pages read by Ananth = \(P - \frac{Pt}{6}\).
  • Pages read by Bharath = Bharath's reading rate \(\times\) time = \(\left(\frac{P}{4}\right) \times t = \frac{Pt}{4}\).
  • Pages remaining for Bharath (\(R_B\)) = Total pages - Pages read by Bharath = \(P - \frac{Pt}{4}\).

Equation Setup for Remaining Pages

The problem states that the number of pages remaining to be read by Ananth is twice that the number of pages remaining to read by Bharath. This can be written as:

\(R_A = 2 \times R_B\)

Substitute the expressions for \(R_A\) and \(R_B\):

\(P - \frac{Pt}{6} = 2 \times \left(P - \frac{Pt}{4}\right)\)

Time Calculation for Remaining Pages

Now, let's solve this equation for \(t\). We can divide both sides by \(P\) (since \(P\) is the total number of pages, it must be greater than 0):

\(1 - \frac{t}{6} = 2 \times \left(1 - \frac{t}{4}\right)\)

Distribute the 2 on the right side:

\(1 - \frac{t}{6} = 2 - \frac{2t}{4}\)

Simplify the term \(\frac{2t}{4}\):

\(1 - \frac{t}{6} = 2 - \frac{t}{2}\)

To solve for \(t\), gather all terms involving \(t\) on one side and constants on the other:

\(\frac{t}{2} - \frac{t}{6} = 2 - 1\)

\(\frac{t}{2} - \frac{t}{6} = 1\)

Find a common denominator for the fractions involving \(t\). The least common multiple of 2 and 6 is 6:

\(\frac{3t}{6} - \frac{t}{6} = 1\)

Combine the fractions:

\(\frac{3t - t}{6} = 1\)

\(\frac{2t}{6} = 1\)

Simplify the fraction:

\(\frac{t}{3} = 1\)

Multiply both sides by 3 to find \(t\):

\(t = 3\)

Answer Verification for Reading Time

Let's check if our calculated time of 3 hours satisfies the condition:

  • Pages remaining for Ananth after 3 hours: \(P - \frac{P \times 3}{6} = P - \frac{P}{2} = \frac{P}{2}\).
  • Pages remaining for Bharath after 3 hours: \(P - \frac{P \times 3}{4} = P - \frac{3P}{4} = \frac{P}{4}\).

Is the number of pages remaining for Ananth twice that of Bharath?

\(\frac{P}{2} = 2 \times \frac{P}{4}\)

\(\frac{P}{2} = \frac{2P}{4}\)

\(\frac{P}{2} = \frac{P}{2}\)

The condition holds true. Therefore, after 3 hours, the number of pages remaining for Ananth is twice the number of pages remaining for Bharath.

Final Resulting Hours

The number of hours after which the pages remaining to be read by Ananth is twice that of Bharath is 3 hours.

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Important Questions from Numerical Computation

  1. A cube of side 3 units is formed using a set of smaller cubes of side 1 unit. Find the proportion of the number of faces of the smaller cubes visible to those which are NOT visible.

  2. What is the average of all multiples of 10 from 2 to 198?

  3. Ratio of the angles of a triangle are 1 : 2 : 6. What is the smallest angle?

  4. A deposit in a bank, which pays interest on its deposits compounded daily, grows to Rs. 80,000 for 500 days and to 88,000 for 1000 days. What would be its value (in Rs.) for 1500 days?

  5. Among A, B, C and D, there is a lawyer, a doctor, a teacher and a journalist. They drink exactly one each of tea, coffee, lemonade and milk. If neither the lawyer nor the teacher drinks milk, B drinks coffee, A is the teacher and C is the doctor and drinks tea, then which of the following is FALSE?

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