You could realize that in order to have the same number of zeros, you would need 000 ( three zeros) so you would have to multiply it for 1.000. After that, you would have 7.200.000, however thats bigger that the number of you need, so try to think about what percentage of the number you woud need.

In this situation you could figure out that you would need about 15% less than your actual number, so you rest 15% of 1.000 and that would be around 850, which is not that far from the answer of 875.

Have in mind that depending on the situation, you would need to do the math calculation exactly and you could not round up the numbers. In this case, just do the traditional division process

Hi Chris,

in the specific example you provided, I would consider the following:

1. Cut unnecessary 00. This reduce the equation to 63.000 / 72
2. Transform the equation in 63/7.2 * 10^2
3. Perform the division of 63 / 7. This will give you 9. Your solution will be thus close to 900
4. As you know the actual divisor is 7.2, you know the first number is 8
5. 7.2*8 =57.6. Thus 5.4 as a difference
6. Repeat previous process. 54/7=7. As this is the second number, solution should be close to 870
7. Continue the process according to the simplification you need

Best,
Francesco

If you feel uncomfortable with divisions, I would just stick with long division technique and keep your neves steady. I second the suggestion of using powers of 10. I would advise against memorizing division tables because under pressure you might misremember, forget and get flustered. Also using methodology suggested under (3) might elica different reactions from interviewer: some might appreciate it, others might not and get ticked off by it (too many roundings and then an arbitrary reverse rounding to correct for it) or, even worse, think you aren’t able to do divisions at all.

If you still would like to use (3) because you feel super-comfortable in remembering the key divisions, but want to avoid potential repercussion would ask for permission before proceeding with it.

Andrea

Dear Chris,

Remember here about estimating and adjusting.

For example: 96,840/529

Step 1: Estimating

We will have a simplified version of: 96.84/52.9, taking out 3 zeros in the numerator and 1 zero in the denominator which means that we will return 2 zeros in the last step.

Technically we need a step of “rounding” here. But in this case, we can just skip it and make an overall adjustment later.

Now turn division into multiplication and find x:

52.9 x ? = ~96.8

We know 53 x 2 = 106

Thus, ? is a little bit lower than 2.

Step 2: Adjusting

With a downward adjustment for 2, we have 1.8. And with zeros, it is 180.

The correct answer is 183.06

Hope it helps,

Best,

André

(editiert)