# Alarm clock

The old watchmaker has a unique digital alarm in its collection that rings whenever the sum of digits of the alarm is equal to 21. Find out when the alarm clock will ring. What is their number? List all options . ..

### Correct answer:

Tips to related online calculators

See also our variations calculator.

Do you want to convert time units like minutes to seconds?

Would you like to compute count of combinations?

Do you want to convert time units like minutes to seconds?

Would you like to compute count of combinations?

#### You need to know the following knowledge to solve this word math problem:

## Related math problems and questions:

- Hello adding

Fill letters instead of digits so the indicated sum (equal letters represent equal digits). What number is hidden under the letter J? A A H A H O A H O J -------------------------- 4 3 2 1 - Number train

The numbers 1,2,3,4,5,6,7,8 and 9 traveled by train. The train had three cars and each was carrying just three numbers. No. 1 rode in the first carriage, and in the last carriage was all odd numbers. The conductor calculated sum of the numbers in the firs - Star equation

Write digits instead of stars so that the sum of the written digits is odd and is true equality: 42 · ∗8 = 2 ∗∗∗ - Clock

What time is now if the time elapsed afternoon is 2/10 of time that elapses before midnight? - All pairs

Determine all pairs (m, n) of natural numbers for which is true: m s (n) = n s (m) = 70, where s (a) denotes the digit sum of the natural number a. - The largest number

Find the largest integer such that: 1. No figures is not repeat, 2. multiplication of every two digits is odd, 3. addition all digits is odd. - Equation algebraogram

Solve the equation: oco + ivo = cita How much has the task of solutions? - Sum of the digits

How many are two-digit natural numbers that have the sum of the digits 9? - Clubhouse

There were only chairs and table in the clubhouse. Each chair had four legs, and the table was triple. Scouts came to the clubhouse. Everyone sat on their chair, two chairs were left unoccupied, and the number of legs in the room was 101. How many chairs - Fluid

We have vessels containing 7 liters, 5 liters and 2 liters. Largest container is filled with fluid the others empty. Can you only by pouring get 5 liters and two 1 liter of fluid? How many pouring is needed? - Chocolate

How many times do we have to break a chocolate bar composed of 10 × 12 pieces to get the 120 parts? - David number

Jana and David train the addition of the decimal numbers so that each of them will write a single number and these two numbers then add up. The last example was 11.11. David's number had the same number of digits before the decimal point, the Jane's numbe - Rings - intersect

There are 15 pupils on the sporting ring. 10 pupils go to football, 8 pupils go to floorball. How many pupils go to both rings at the same time? - Unknown number 24

I think the number: a - is the same as the square area that has the 12th circumference. What is this number? b - its half is 7 times bigger than its quarter. Is this the number? - A five-digit

A five-digit odd number has the sum of all digits (digits) five and contains two zeros. If we move each digit in the number one place to the left and move the first digit to the last place, we get a number 20,988 smaller. Find this unknown five-digit numb - Six-digit primes

Find all six-digit prime numbers that contain each one of digits 1,2,4,5,7, and 8 just once. How many are they? - Seven-segmet

Lenka is amused that he punched a calculator (seven-segment display) numbers and used only digits 2 to 9. Some numbers have the property that their image in the axial or central symmetry was again give some number. Determine the maximum number of three-di