Revision for the Grade 8 maths exam does not have to be stressful. Making flashcards, memorising maths key facts, or memorising the repeating decimal to fraction number can help you as you prepare for the coming maths exams.
Below are key facts and maths skill that you can master in 10 minutes. The multiplication and division tricks and tips below will make a world of difference when you take the Grade 8 maths exam.
1 is not a prime number
For a number to be a prime number it must have only two factors, 1 and itself. 1 has only 1 factor, 1.
First 10 prime numbers: 2,3,5,7,11, 13,17, 19, 23,…
- 9 is odd number, not prime number with factors {1,3,9}
- 15 is odd number, not prime number with factors {1,3,5,15}
List of common and repeating decimal to fraction and percentages
½=50%=0.5
⅓=33⅓%=33.3…
¼=25%=0.25
⅕=20%=0.2
⅛=12.5%=0.125
¹/10=10%=0.1
⅔=66⅔%=66.6…
⅖=40%=0.4
¾=75%=0.75
⅗=60%=0.6
Take the online Fraction Quiz to test your knowledge.
[qsm_link id=1]Click here[/qsm_link]
×12 Recall Tip
12×1=1 2
12×2=2 4
12×3=3 6
12×4=4 8
12×5=6 0
12×6=7 2
12×7=8 4
12×8=9 6
12×9=10 8
12×10=12 0
12×11=13 2
12×12=14 4
- Starting numbers increase in 1,2,3…*
- Multiples of ×12 end in 0,2,4,6 or 8 and reoccur after 5 numbers
- Only applies to ×12
Add 3-digit numbers
123 + 573
=(100 + 20 + 3) + (500 + 70 + 3)
= 100 + 500 + 20 + 70+ 3 + 3
= 600 + 90 + 6
= 696
Mental tips for division by a decimal
270 ÷ 0.3
🚦make 0.3 whole number by × 10
I.e. 270 × 10 = 2700; 0.3 ×10= 3
Now, 2700 ÷ 3 = 900
Top tip: In division by decimals, multiply the dividing numbers by 10, 100,… to change decimal numbers to whole numbers
#NumberSkills #CoolTips
Dividing with decimal numbers
E.g. 80÷1.5
🚦×10 make 1.5 whole
80×10=800; 1.5×10=15
–‐‐—————-‐–
🚦simplify
800÷15… ÷5
=160÷3
🚦partition 160…150+10
(150÷3)+(10÷3)
=50+3⅓
=53⅓ (or 53.33…)
*Tip: make the decimal a whole number; then simplify, partition and solve.
Dividing 3-digit numbers
836 ÷ 32
🚦split 836 into easily divisible numbers
|640 | 160 | 32 | 4 …sum is 836
÷| 32 | 32 | 32 | 32 …divisor is 32
——–‐‐——————-
20 + 5 + 1 + ⅛ = 26⅛ or 26.125
Tip: Go by 20, 10, 5 to reduce 3 digit numbers like 836. You can also apply the same technique to simplify even bigger numbers.
#NumberFacts
Mental multiplication of big numbers
53 × 37
○ 50 | 30
● 3 | 7
-‐——————-‐–
○50×30=1,500
○50×7= 350
●3×30= 90
●3×7= 21
————————-
1,500 + 350 + 90 + 21 = 1,961
#MentalMathTips
Long multiplication of big numbers
53 × 37
———–
53
×37
””””””’
371
+ 159
””””””””””
1961 …answer
Divide with Common and Repeating Decimal to Fraction
E.g.280 ÷ 3½
🚦Convert fraction to decimal 3½=3.5
280÷3.5
🚦multiply 280 and 2.5 by 10 to make 3.5 whole numbers before dividing.
= 2,800÷35
💡35 × 8 = 280
If 35×8=280🔁280÷35=8, so 2800÷35=80
———————-
So, 280÷3½
=280÷3.5
=2,800÷35
=80
#MentalDivision
Basic maths skills: Tips and Study Guides
We have a collection of Grade 8 topics and study guides that you might find useful when planning for the year or just brainstorming the maths course. Check it out.
Check out the Home page for links to our collections of Grade 8, Grade 10 and Grade 12 exam papers.
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