Given information:
- The number of girls in the class is twice the number of boys.
- Each student contributes as many rupees as there are boys.
- The total contribution is Rs 2352.

Let's solve the problem step by step:

Step 1: Understanding the problem:
- We need to find the number of boys and girls in the class.
- We also need to find the amount contributed by each student.

Step 2: Let's assume:
- Let's assume the number of boys in the class is 'x'.
- According to the given information, the number of girls will be twice the number of boys, so the number of girls will be '2x'.

Step 3: Contribution:
- Each student contributes as many rupees as there are boys. So, each boy contributes 'x' rupees and each girl contributes '2x' rupees.
- The total contribution is Rs 2352, so we can form the following equation:
- Contribution by boys + Contribution by girls = Total contribution
- (x * x) + (2x * 2x) = 2352
- x^2 + 4x^2 = 2352
- 5x^2 = 2352

Step 4: Solving the equation:
- We need to solve the equation 5x^2 = 2352 to find the value of 'x' (number of boys).
- Dividing both sides of the equation by 5: x^2 = 470.4
- Taking the square root of both sides: x = √470.4
- Calculating the square root: x ≈ 21.68

Step 5: Calculating the number of girls:
- The number of girls is twice the number of boys.
- Number of girls = 2x = 2 * 21.68
- Number of girls ≈ 43.36 ≈ 43 (approx.)

Step 6: Calculating the contribution:
- Each boy contributes 'x' rupees, which is approximately 21.68 rupees.
- Each girl contributes '2x' rupees, which is approximately 43.36 rupees.

Step 7: Checking the total contribution:
- Total contribution = (Number of boys * Contribution per boy) + (Number of girls * Contribution per girl)
- Total contribution = (21.68 * 21.68) + (43.36 * 43.36)
- Total contribution ≈ 470.4 + 1880.96
- Total contribution ≈ 2351.36 ≈ 2352 (approx.)

Step 8: Conclusion:
- The number of boys in the class is approximately 21.
- The number of girls in the class is approximately 43.
- Each boy contributes approximately Rs 21.68.
- Each girl contributes approximately Rs 43.36.
- The total contribution is Rs 2352, which matches the given information.

Therefore, the true statement is that the number of boys in the class is approximately 21.