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How do you measure 9 minutes with a 4 and 7 minute hourglass?
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 do you measure 15 minutes to boil an egg if there are 2 kinds of hourglass 11 minutes 7 minutes?
Explanation: To boil the egg in exactly 15 minutes, follow these steps.
- Start both hourglasses as you start boiling the egg.
- After the 7-minute hourglass runs out, turn it to start it again.
- Four minutes later, when the 11-minute hourglass runs out, turn the 7-minute hourglass again.
How do you measure 15 minutes to boil an egg if there are 2 kinds of hourglass?
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.
How long does it take for an hourglass to empty?
In its usual form it consists of two cone-shaped or oval glass receptacles joined by a narrow neck. Sand or a liquid (such as water or mercury) in the uppermost section of a true hourglass will run through the neck into the lower section in exactly one hour.
How do you boil an egg for 15 minutes?
Place 12 eggs in the bottom of a large pot and and cover with water 1 inch above the eggs. Bring the water to a boil, gently stirring the eggs several times. As soon as the water boils, remove the pot from the heat, cover, and let the eggs sit for 15 minutes (13 minutes for small eggs or 17 minutes extra large eggs).
What happens if you boil eggs for 15 minutes?
Hard-cooked (boiled) eggs – 19 minutes If you cook them for too long, the protein toughens (becomes rubbery) and a greenish or purplish ring forms around the yolk. Extremely fresh eggs are not recommended when making hard-boiled eggs, as they are very difficult to peel.
What is sand clock class 7?
Sand clock is also known as sand-glass or hour-glass. The sand clock uses the flow of sand (from one glass bulb to another) to measure time. The length of time taken by the sand to pass from one bulb of the sand clock to the other, gives a constant time interval.
Is an hourglass an hour?
Hourglass, a device for measuring time. Sand or a liquid (such as water or mercury) in the uppermost section of a true hourglass will run through the neck into the lower section in exactly one hour. By turning the other end up, another hour may be marked, and the process may be continued indefinitely.