How do you measure 15 minutes?

When the 7 minute hourglass runs out, there are 4 minutes left on the 11 minute hourglass. Start your measurement period. When the remaining 4 minutes on the 11 minute hourglass are through, turn the 11 minute hourglass over. When it’s done, you’ve timed 4 + 11 = 15 minutes.

How do you measure 9 minutes using a 7 minute and 4 minute sand clock?

When the 4-min timer is empty for the second time, the 7-min timer has 1 minute worth of sand in the bottom half. Flip it over so there is now 1 minute in the top. When the 7-min timer empties, 9 minutes have elapsed.

How can you use the timers to find out when exactly 15 minutes has passed?

When the 7-minute hourglass runs out put it aside. You will have 4 minutes left in the 11-minute hourglass. That starts your 15 minutes. Let the 4 minutes run out and then turn the 11–minute hourglass over and after it empties 15 minutes will have run by.

How do you measure a 15 minute boiled egg?

Turn over BOTH hourglasses at the same time. When the 7 minute glass is done, there is 4 minutes left on the 11 minute glass. Start cooking the egg. When the 4 minutes has elapsed, turn it over again until done (11 minutes) for a total of 15 minutes.

How can you cook an egg for exactly 15 minutes?

After it empties, turn the small glass, start boiling your eggs and continue watching the big glass. When, at the end of 11 minutes, the big one empties the small glass will be running for 4 minutes. Turn the big glass and wait another 11 minutes. 4 + 11 = 15.

Does sand clock measure time interval?

Explanation: You can use a sand clock to measure time interval only. As a sand clock measure a hour one time, it can’t measure time like 30minutes, 45 minutes, etc.

Are sand timers accurate?

Hourglasses are aesthetically pleasing ornaments, rather than accurate timepieces – most of our hourglasses (except fillable ones) are accurate to within +/- 10\%.

What is the total time elapsed so far in sand timer?

So time elapsed now is 7. Time left in 11 minutes sand timer is 4.Now again 7 minutes sand timer and remaining 11 minutes timer will be started.So after 4 minutes 11 minutes sand timer will be empty and 3 minutes time of sand remaining in 7 minutes sand timer. Total time elapsed so far is 11 minutes.

How long does it take to empty the sand?

This Puzzle is one of the most commonly asked interview puzzle. Problem: You have two sand timers with you. One can measure 7 minutes and the other sand timer can measure 11 minutes. This means that it takes 7 minutes for the sand timer to completely empty the sand from one portion to the other. You have to measure 15 minutes using both the timers.

How do you measure 15 minutes on a sand hourglass?

Before beginning your 15 minute measurement, turn both hourglasses. When the 7-minute one runs out, bring the 11-minute one to rest, ie turn it on its side so no sand flows in either direction. You then have 4 minutes of sand remaining in one side of the hourglass.

How do you use the 7 minute and 11 minute hourglass?

The 7 minute hourglass will run out after 7 minutes, of course, leaving 4 minutes in the 11 minute hourglass. Turn over the 7 minute hourglass as soon as it runs out. After 11 minutes, the 11 minute hourglass will run out. The 7 minute hourglass will have 4 minutes worth of sand in the bottom.