Rounding Off Numbers

Find a 9-digit number, which you will gradually round off starting with units, then tenth, hundred etc., until you get to the last numeral, which you do not round off. The rounding alternates (up, down, up ...). After rounding off 8 times, the final number is 500000000. The original number is commensurable by 6 and 7, all the numbers from 1 to 9 are used, and after rounding four times the sum of the not rounded numerals equals 24.




Similar Math Riddles

A high school has a strange principal. On the first day, he has his students perform an odd opening day ceremony:

There are one thousand lockers and one thousand students in the school. The principal asks the first student to go to every locker and open it. Then he has the second student go to every second locker and close it. The third goes to every third locker and, if it is closed, he opens it, and if it is open, he closes it. The fourth student does this to every fourth locker, and so on. After the process is completed with the thousandth student, how many lockers are open?

Principal in the School

Asked by Neha on 05 Mar 2021


John was running from 40 thieves. John has got 3 gold boxes which weigh as 4kg, 2kg, and 1kg respectively. A witty man asked John to stay with him for seven days in exchange for 1kg gold per day. John needs to stay there for seven days and also do not want to give the witty man any advance. How can John pay for his seven days stay?

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Using four sevens (7) and a one (1) create the number 100. Except for the five numerals, you can use the usual mathematical operations (+, -, x, :), root and brackets ()

Asked by Neha on 26 May 2023


Can you find the least possible number such that

If the number is divided by 3, it gives the remainder of 1;
If the number is divided by 4, it gives the remainder of 2;
If the number is divided by 5, it gives the remainder of 3;
If the number is divided by 6, it gives the remainder of 4.

Asked by Neha on 23 Oct 2024

In a classic wine shop, the list of three most popular wines are:
- The cost of 1 French wine bottle: 500$
- The cost of 1 German wine bottle: 100$
- The cost of 20 Dutch wine bottles: 100$

John entered the wine shop and he needs to buy
- All three types of wine bottles.
- Needs to buy Dutch wine bottles in multiples of 20.
- Need to buy 100 wine bottles in total.

John has only 10000$. How many wine bottles of each type, John must buy?

Asked by Neha on 19 Aug 2023

Chocolate costs 6 rupees and a Toy costs 5 rupees. If you have 32 rupees in total, how many chocolates and how many Toys can be purchased with that amount?

Asked by Neha on 02 Mar 2025


A famous swimmer can swim downstream in a lake in exactly 40 minutes with the lake current.
He can swim upstream in that lake in exactly 60 minutes against the lake current.
The length of the lake is 2 km.

How long he can cover the distance of one side at a still lake with no current?

Asked by Neha on 27 Nov 2025

Double it and multiply it by 4. Then divide it by 8 and you’ll have it once more. What number is it?

Asked by Neha on 23 Oct 2025

If one and a half boys, eat one and a half burgers in one and a half hours.

How many burgers can 9 boys eat in 3 hours?

Asked by Neha on 20 May 2023


A and B have a certain number of chocolates with them. If B gives one chocolate to A, they will have an equal number of chocolates. But if A gives one chocolate to B, then A will be left with half the number of chocolates that B has.

Can you find out the number of chocolates they have right now?

Asked by Neha on 02 Apr 2023

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In 2007, a puzzle was released and $2 million prizes were offered for the first complete solution. The competition ended at noon on 31 December 2010, with no solution being found. Wiki