4/10 as a Decimal

Terminating decimal · 40.00% · simplified 2/5

4/10 = 0.4. The division comes to rest after 1 decimal place, so you can write the whole value without a bar or an approximation. As a percentage that is 40.00%.

Long division, step by step

Divide the numerator by the denominator the way it is done on paper: bring down a zero, note how many times the denominator fits, keep the remainder, repeat. The remainders are what decide whether the decimal stops.

The remainder reaches zero at step 1, which is precisely why the decimal terminates. A zero remainder means nothing is left to carry down.

Rounded to different precisions

How many places you keep depends on the use: money stops at two, engineering often wants three or four, and a science problem usually wants significant figures rather than decimal places.

Will it terminate?

A fraction has a terminating decimal exactly when its simplified denominator is built only from 2s and 5s. Here the denominator reduces to 5, which factors to 5 — nothing but 2s and 5s, so the decimal stops. This is a property of the denominator alone: the numerator never decides it.

Because 4/10 reduces to 2/5, the recurrence pattern is the same as for 2/5. Simplifying first is the quickest way to see the true period.

Questions about 4/10

What is 4/10 as a decimal?

Exactly 0.4. The division terminates because the reduced denominator 5 has no prime factors other than 2 and 5, so the decimal stops after 1 digits.

Is 4/10 already in simplest form?

No. Dividing both parts by their greatest common factor gives 2/5, which has the same value and a shorter representation.

How do I round 4/10 to two decimal places?

Two places give 0.4. The exact value is already closed at 1 digits, so rounding only pads or trims zeros rather than changing the value.

What is 4/10 as a percentage?

40.00%, obtained by multiplying the decimal by 100. It is the same number with the decimal point moved two places to the right, and the same rounding rules apply.