Decimals: Reading, Comparing and Doing the Math
What decimals are, the place values (tenths, hundredths, thousandths), how to read, compare, add and multiply them, and how to turn a fraction into a decimal, with worked examples.
By Polarzinho ·
The Plop! screen shows multipliers like x1.5 and x1.25. Those numbers have a whole part and a broken part: they are decimals.
Here is everything to understand decimals: the place values, how to read, compare, add and multiply them, and how to turn a fraction into a decimal. All the math was done with whole numbers, with no rounding.
What is a decimal?
A decimal has a whole part and a decimal part, separated by a point. The part after the point shows pieces of a whole: 0.5 is a half, 0.25 is a quarter.
Place values
Each digit is worth ten times less than the one to its left. In the number 2.375:
- 2 is in the ones place: 2 wholes.
- 3 is in the tenths place: 3 tenths.
- 7 is in the hundredths place: 7 hundredths.
- 5 is in the thousandths place: 5 thousandths.
How to read a decimal
- 0.1: one tenth, or "zero point one".
- 0.5: five tenths, or "zero point five".
- 0.25: twenty-five hundredths, or "zero point two five".
- 0.125: one hundred twenty-five thousandths.
- 1.5: one and five tenths, or "one point five".
From a fraction to a decimal
Divide the numerator by the denominator:
- 1/2 = 0.5
- 1/4 = 0.25
- 3/4 = 0.75
- 1/5 = 0.2
- 3/5 = 0.6
- 1/8 = 0.125
How to compare decimals
- 0.5 is greater than 0.25: 5 tenths are 50 hundredths, and 50 is more than 25.
- 0.3 and 0.30 are the same number: a zero at the end of the decimal part does not change the value.
- 1.09 is less than 1.1: compare place by place, from left to right.
Adding, subtracting and multiplying
- Adding: line up the points. 2.5 + 1.25 = 3.75.
- Subtracting: line up the points too. 4 − 1.5 = 2.5.
- Multiplying by 10 or 100 moves the point: 2.5 × 10 = 25 and 0.25 × 100 = 25.
- Multiplying by 1.5 means adding half: 40 × 1.5 = 40 + 20 = 60.
- Multiplying by 1.25 means adding a quarter: 40 × 1.25 = 40 + 10 = 50.
Decimals in Plop!
The multipliers on the Plop! screen, like x1.5 and x1.25, are decimals. On the same screen, the score shows a whole number, 532, and the juice meter has marks at round numbers.
Polarzinhox1.5 and x1.25: two decimals, two smiles.
FAQ
How do you read 0.25?
Twenty-five hundredths, or "zero point two five".
How do you turn a fraction into a decimal?
Divide the numerator by the denominator. For example, 3/4 = 0.75.
Is 0.5 equal to 0.50?
Yes. Zeros at the end of the decimal part do not change the value.
Which is greater, 0.3 or 0.25?
0.3, because 0.30 is greater than 0.25.
Your turn
What is 0.75 + 0.5? Which is greater, 0.4 or 0.35? And 3/5 as a decimal? Answers: 1.25, 0.4 and 0.6.