Chapter 4.3, Problem 16PSC

To determine

To calculate: To find that after 7:00, when angle between hands of clock are at right angle first time.

Answer to Problem 16PSC

7 hours 21 minute 49 seconds

Explanation of Solution

Given information: After 7:00, angle between minutes hand ad hour had is ${90}^{\circ }$ for the first time.

Formula used: At X hour y minutes, angle between hands of clock is $\left|\frac{60X-11Y}{2}\right|.$

Calculation: Given X=7. Using the formula,

  $\begin{array}{l}\left|\frac{60\times 7-11Y}{2}\right|={90}^{\circ }\\ \therefore 420-11Y={180}^{\circ }\\ \therefore Y=\frac{240}{11}\\ \therefore Y=21\text{'}49"\end{array}$