A ball is thrown vertically upwards from ground with such a speed so that it just reaches the top of a building and then falls back. If it takes 7s for the ball to return to the hands of thrower. Calculate the height of the building approximately.

Explanation

To solve the problem, we need to analyze the motion of the ball thrown vertically upwards and then falling back down to the thrower's hands. Here’s a step-by-step solution:

### Step 1: Understand the total time of flight
The total time taken for the ball to return to the thrower's hands is given as 7 seconds. Since the ball goes up and then comes back down, the time taken to reach the highest point (top of the building) is half of the total time.

**Calculation:**
\[
\text{Time to reach the top} = \frac{7 \text{ s}}{2} = 3.5 \text{ s}
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