The four operations and negative numbers
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 8 practice questions, 1 real past-paper question with the answer explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Below zero
- Adding and subtracting
Read the transcript of the teaching part
Last time
Before we start: last time, in Fractions and mixed numbers, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Below zero
A bank balance of minus thirty-five dollars. A freezer at minus eighteen degrees. Negative numbers are everywhere. Today you will add, subtract, multiply and divide them without slips. Then you will meet the order of working that decides every calculation.
Adding and subtracting
Adding moves you right along the number line. Minus four plus nine is five. Subtracting a positive moves you left. Minus four minus nine is minus thirteen. Here is the key rule: subtracting a negative is the same as adding. Six minus minus nine is six plus nine. So six minus minus nine is fifteen. Two minus signs side by side turn into a plus.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Decimals and the order of · Negative numbers and number · Types of number.
The whole chapter: Numbers and the Four Operations.
Chapter 1: Number
- Number families, reciprocals and ordering 6 min
- The four operations and negative numbers 5 min
- Primes, factors and prime factor trees 5 min
Also for O Level Maths 4024
Which topics come up most in O Level Maths 4024 past papers, counted from every paper since 2004.