What you need to know

Things to remember:

  • Adding a zero to the end of a decimal number won’t change its value.
  • We can add zeros to the end of decimal numbers so that they have the same number of digits after the decimal point.

Put the following decimals in order from biggest to smallest.

25.178                         25.9                 25.32                           25.19                           25.77

Well, this is easy right? 25.178 must be the biggest, look at all those digits! And look at 25.9, it is tiny compared to the others… Not quite! This is the problem, we can’t compare the numbers based on how many digits they have. So, let’s make sure they all have the same number of digits before we try to compare them.

Hint: Remember, we can put 0s at the end of decimals without changing its actual value.

 

25.178

25.900

25.320

25.190

25.770

Now that they have the same number of digits, we can compare them a lot more easily. Because they have the same whole number part, we can just ignore them and focus on the decimal. If we notice how they all now look like “hundreds”, we can just compare them how we normally would.

25.900             25.9

25.770             25.77

25.320             25.32

25.190             25.19

25.178             25.178

So, funnily enough, 25.9 was the biggest number, and 25.178 was the smallest!

Example Questions

Question 1: Put the following decimal numbers in order from smallest to biggest:

 

4.23                 4.7                   4.65                 4.256               4.55

Answer

4.230               4.23

4.256               4.256

4.550               4.55

4.650               4.65

4.700               4.7

Question 2: Choose the biggest number from of the following list:

 

4.35                 5.01                 4.78                 3.9984             2.9984

Answer

We need to be careful here. Although 3.9984 and 2.9984 have the biggest decimals, the whole number parts are small than the other numbers.

 

5.01 is biggest