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Mathematics chapter guide

SPM Mathematics number bases: where to start

Numbers you know well suddenly use new digits, and every carry feels like a trap.

The number bases chapter shows that our ordinary counting is only one way of writing numbers. You learn to write the same quantity in another base, to convert between bases, and to add and subtract in them.

The chapter sits in SPM Mathematics and is part of the Form 4 Mathematics topics.

How do the four lessons connect?

All four rest on place value, which is why the order matters.

  1. Converting base ten to another base teaches place value in a new base.
  2. Converting between non-decimal bases shows how to go from one new base to another.
  3. Adding and subtracting numbers in different bases uses the column method with the new base.
  4. Checking place-value errors in base conversions gives you ways to verify every answer.

What does one small number show?

Take 13 in base ten. In base two, the place values are 8, 4, 2 and 1, so 13 = 8 + 4 + 0 + 1, which is written 1101₂.

Add 1 to 1101₂: the units column makes 2, which is 10₂, so it carries once. The result is 1110₂, which is 14. Place value, conversion, addition and checking all appear in this one small number.

Who should start where?

If you are not sure why 1101₂ equals 13, begin at lesson one. If you can convert but the carries go wrong, start at lesson three. If your answers come out with digits that do not exist in the base, such as a 5 in base five, lesson four will help.

Test yourself with the number bases practice set.

When does extra help make sense?

Number base errors are small and systematic, and they often come from one habit, such as carrying ten. A teacher who sees your columns can name the habit quickly.

If that sounds useful, see online one-to-one Mathematics tuition and mention number bases when you enquire.

Common questions

What does a small number beside a number mean, like 213₅?

The small number is the base. It tells you that the place values are powers of 5 and that the only digits allowed are 0 to 4. Without a base, a number is read as base ten.

Which lesson should I start with?

Start with converting base ten to another base, because it teaches place value in a new base. Every later lesson reuses that idea.

Why do students lose marks in number bases?

Usually the error is using ten in a column where the base is needed, such as carrying 10 instead of the base. A base-ten check at the end catches it.

Do I need to memorise powers of the bases?

Know the first few powers of the bases in your questions, such as 2, 4, 8, 16 and 32 for base two. Write them at the top of your working so you need not recall them under pressure.

If base conversions go wrong at the carry step, a one-to-one Mathematics teacher can watch your column working on your own questions and show the exact place the base is forgotten.

  • Online one-to-one lessons for your child with an experienced teacher.
  • Your first class is a one-hour trial, from RM50. The fee is agreed before you book.
  • Happy with the teacher? Continue with lessons of about 1.5 hours. If not, ask for another teacher.