# To perform mental calculations

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## Memorandum

1. NUMBER CONCEPT

1.1 27

1.2 79

1.3 96

1.4 63

1.5 42.5

1.6 3.2

1.7 100

1.8 300

1.9 294

1.10 992

1.11 8

1.12 55

1.13 63

1.14 +

1.15 445

## Solve the following puzzle

 B C E H I M N O P R T U 17 11 5 14 21 7 2 6 8 4 18 12

## Clues:

 1. 24 ÷ 12 8. 36 ÷ 6 2. 5 + 7 9. 14 ÷ 7 3. 11 - 4 10. 17 − 6 4. 8 + 9 11. 25 ÷ 5 5. 20 ÷ 4 12. 2 × 4 6. 13 − 9 13. 27 − 9 7. 20 - 9

## Activity: to perform mental calculations [lo 1.9.1, lo 1.9.2]

1. In Mathematics it is important to be able to think fast. Let’s see how quick you are in your first mental arithmetic test in Grade 6. Work as quickly and as accurately as possible.

## 1. think fast!

In Mathematics it is important to be able to think fast. Let’s see how quick you are in your first mental arithmetic test in Grade 6. Work as quickly and as accurately as possible.

 1.1 56 + ................. = 83 1.4 .................  9 = 7 1.2 49 × 15 = ................. 1.5 Halve 85: ................. 1.3 12 × 8 = ................. 1.6 Double 163: ................. 1.7 20 × ................. = 2 000 1.12 A half × ................. = 150 1.8 (7 × 9) − 8 ................. 1.13.. (38 + 49) − 24 = ................. 1.9 98 + 99 + 97 = ................. 1.14 89 ................. 16 = 105 1.10 1 004 − 12 = ................. 1.15 998 − ................. = 550 1.11 8 × 9 × 6 = 6 × ............ × 9

Complete: I have _____________________________________ correct!!

## Did you know?

Can you remember what numbering system we make use of today?

____________________________________________________________________

The ancient Romans developed their counting system more than 2 000 years ago and some of their numbers looked like this: I ; II ; III ; IV ; V

## 2. let’s count

Work with a friend and take turns to count in:

2.1 tens from 19 870 to 20 040

2.2 hundreds from 67 403 backwards to 65 903

• thousands from 37 556 backwards to 29 556
• ten thousands from 25 526 to 95 526

## Assessment

Learning Outcome 1: The learner will be able to recognise, describe and represent numbers and their relationships, and to count, estimate, calculate and check with competence and confidence in solving problems.

Assessment Standard 1.9: We know this when the learner performs mental calculations involving:

1.9.2: multiplication of whole numbers to at least 12 x 12.

what is math number
x-2y+3z=-3 2x-y+z=7 -x+3y-z=6
Need help solving this problem (2/7)^-2
x+2y-z=7
Sidiki
what is the coefficient of -4×
-1
Shedrak
the operation * is x * y =x + y/ 1+(x × y) show if the operation is commutative if x × y is not equal to -1
An investment account was opened with an initial deposit of \$9,600 and earns 7.4% interest, compounded continuously. How much will the account be worth after 15 years?
lim x to infinity e^1-e^-1/log(1+x)
given eccentricity and a point find the equiation
12, 17, 22.... 25th term
12, 17, 22.... 25th term
Akash
College algebra is really hard?
Absolutely, for me. My problems with math started in First grade...involving a nun Sister Anastasia, bad vision, talking & getting expelled from Catholic school. When it comes to math I just can't focus and all I can hear is our family silverware banging and clanging on the pink Formica table.
Carole
I'm 13 and I understand it great
AJ
I am 1 year old but I can do it! 1+1=2 proof very hard for me though.
Atone
hi
Not really they are just easy concepts which can be understood if you have great basics. I am 14 I understood them easily.
Vedant
find the 15th term of the geometric sequince whose first is 18 and last term of 387
I know this work
salma
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
hmm well what is the answer
Abhi
If f(x) = x-2 then, f(3) when 5f(x+1) 5((3-2)+1) 5(1+1) 5(2) 10
Augustine
how do they get the third part x = (32)5/4
make 5/4 into a mixed number, make that a decimal, and then multiply 32 by the decimal 5/4 turns out to be
AJ
how
Sheref
can someone help me with some logarithmic and exponential equations.
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
hmm
Abhi
is it a question of log
Abhi
🤔.
Abhi
I rally confuse this number And equations too I need exactly help
salma
But this is not salma it's Faiza live in lousvile Ky I garbage this so I am going collage with JCTC that the of the collage thank you my friends
salma
Commplementary angles
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
hii
Uday
hi
salma
hi
Ayuba
Hello
opoku
hi
Ali
greetings from Iran
Ali
salut. from Algeria
Bach
hi
Nharnhar
A soccer field is a rectangle 130 meters wide and 110 meters long. The coach asks players to run from one corner to the other corner diagonally across. What is that distance, to the nearest tenths place.
Jeannette has \$5 and \$10 bills in her wallet. The number of fives is three more than six times the number of tens. Let t represent the number of tens. Write an expression for the number of fives.
What is the expressiin for seven less than four times the number of nickels
How do i figure this problem out.
how do you translate this in Algebraic Expressions
why surface tension is zero at critical temperature
Shanjida
I think if critical temperature denote high temperature then a liquid stats boils that time the water stats to evaporate so some moles of h2o to up and due to high temp the bonding break they have low density so it can be a reason
s.
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
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