Question:medium

If the eccentricity and length of latus rectum of a hyperbola are \(\frac{\sqrt{13}}{3}\) and \(\frac{10}{3}\) units respectively, then what is the length of the transverse axis?

Show Hint

Whenever you are given both eccentricity and the latus rectum, you can find the semi-major axis \(a\) rapidly by noticing that \(\text{Latus Rectum} = 2a(e^2 - 1)\). Substituting the given values: \(\frac{10}{3} = 2a\left(\frac{13}{9} - 1\right) \implies \frac{10}{3} = 2a\left(\frac{4}{9}\right) \implies a = \frac{15}{4}\). Multiplying by 2 immediately yields \(\frac{15}{2}\).
Updated On: May 29, 2026
  • \( 7/2 \text{ unit} \)
  • \( 12 \text{ unit} \)
  • \( 15/2 \text{ unit} \)
  • \( 15/4 \text{ unit} \)
Show Solution

The Correct Option is C

Solution and Explanation

Step 1: Understanding the Question:
This question comes from the topic of conic sections, specifically the properties of a hyperbola.
We are given the eccentricity and the length of the latus rectum of a hyperbola, and we need to calculate the length of its transverse axis.
Step 2: Key Formulas and Approach:
Latus Rectum Formula: $\text{L.R.} = \frac{2b^2}{a}$

Eccentricity Relation: $e^2 = 1 + \frac{b^2}{a^2}$

Transverse Axis Length: The length of the transverse axis is equal to $2a$.

Our approach will be to express $b^2$ in terms of $a$ using the latus rectum equation, substitute it into the eccentricity equation, and solve for $a$.

Step 3: Detailed Explanation:

Set up the Latus Rectum Equation:
We are given that the length of the latus rectum is $\frac{10}{3}$:
\[ \frac{2b^2}{a} = \frac{10}{3} \quad \implies \quad b^2 = \frac{5a}{3} \quad \cdots (1) \]
Set up the Eccentricity Equation:
We are given the eccentricity $e = \frac{\sqrt{13}}{3}$. Squaring both sides:
\[ e^2 = \frac{13}{9} \] Using the eccentricity relationship:
\[ \frac{13}{9} = 1 + \frac{b^2}{a^2} \quad \implies \quad \frac{b^2}{a^2} = \frac{13}{9} - 1 = \frac{4}{9} \quad \cdots (2) \]
Solve for $a$:
Substitute the expression for $b^2$ from equation (1) into equation (2):
\[ \frac{\left(\frac{5a}{3}\right)}{a^2} = \frac{4}{9} \] \[ \frac{5}{3a} = \frac{4}{9} \] \[ 27 a = 45 \quad \implies \quad a = \frac{45}{12} = \frac{15}{4} \]
Calculate the Length of the Transverse Axis:
The length of the transverse axis is $2a$:
\[ \text{Length} = 2 \times \frac{15}{4} = \frac{15}{2}\text{ units} \]
Step 4: Final Answer:
The length of the transverse axis of the hyperbola is $15/2$ units, which corresponds to Option (C).
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