ALGEBRA: Open Sentence

LESSON 3

ALGEBRA: Use of Letters in Mathematics 3

OPEN SENTENCE

This is a mathematical statement in which numbers and boxes(SPACE) are used. The boxes(SPACE) represent the unknown quantities (amounts).

EXAMPLE 1

3 + [ ] = 10

This open sentence above means 3 plus an unknown number equals 10

Guess what the unknown number is. Yes? Good! You got it!

3 + 7 = 10

See?   The unknown number is 7.

EXAMPLE 2 

What number will make the open sentence below true?

[ ] - 2 = 5

SOLUTION

[ ] - 2 = 5

This open sentence means that when 2 is subtracted from an unknown number the result is 5. When 2 is subtracted from 7 the result is 5.

Therefore, the unknown number is 7!

7 – 2 = 5

EXAMPLE 3

What number will make the open sentence below true?

 4 + 2 = [ ]
                  

SOLUTION

4 + 2 = [ ] 

                  

This open sentence means that the result of 4 plus 2 is unknown. But 4 plus 2 is 6.

Therefore, the unknown result is 6!

4 + 2 = 6

PUSH IT IN!

Now, you know what an open sentence is.

But do you know how to determine the unknown in an open sentence?

Answer true or false to the following statements:

1. When 5 is added to 6 the result is 11.
2. 2 plus 7 is 10.
3. 8 minus 6 is 2.
4. When 3 is removed from 9 the answer is 6.
5. 4 plus 3 is 8.

The answer to the true/false statements above is given below. If you got all the answer correctly then you have mastered how to determine the unknown in an open sentence. Go to the ACTIVITY and have fun! If you got any of the answers wrong, send me a COMMENT and let’s discuss it.

Answer: TRUE, FALSE, TRUE, TRUE, FALSE.

ACTIVITY

In each open sentence below, find the number which makes it true.

1. 9 + 5 = [ ]     
2. [ ] = 6 +3
3. 7 - [ ] = 3
4. [ ] - 5 = 7
5. [ ] + 4 = 9

Post the solution as a COMMENT to this lesson. Include your name or nickname and email because every COMMENTS will be replied. I’m expecting your COMMENT.

 

Congratulation! You've completed this lesson. Now let's go to LESSON 4: TURNING OPEN SENTENCE INTO ALGEBRAIC SENTENCE.

ALGEBRA: Algebraic Sentence

LESSON 2
ALGEBRA: Use of Letters in Mathematics 2

ALGEBRAIC SENTENCE
This is a mathematical statement written with a combination of letters and numbers.

Example 1:

Mathematical statement: John's transport allowance is the same as Jane's feeding allowance.

Let y represents John's transport allowance and

      x represents Jane's feeding allowance.

The relation is equal to (=) 

John's transport allowance = Jane's feeding allowance

Algebraic sentence:
y = x

Example 2:

Mathematical statement: Olu has some balls in a basket and Chima brought 2 more balls and place them in the same basket. How much balls are in the basket altogether?

Let m represents the number of Olu's balls inside the basket.

The relation is addition (+) 

the number of Olu's ball + the number of Chima's ball(2)

Algebraic sentence:
m + 2

Example 3:

Mathematical statement: A trader has a number of bags of rice in his shop. He sold 6 bags of rice. What is the number of bag of rice left in his shop?

Let u represents the number of bag of rice in the traders shop.

The relation is subtraction (-)

the number of bag of rice in the shop - the number of bag of rice sold(6) 

Algebraic sentence:
u - 6

Example 4:

Mathematical statement: If the cost of a book is N400, what is the cost of p number of books.

The number of books = p

The cost of one book = N400

The relation is multiplication(x)

the cost of one book(N400) x the number of books(p)

Algebraic sentence:
N400 x p  
Or N400p

Example 5:

Mathematical statement: q Naira was shared equally amongst 8 children. What does each child gets?

The amount of money shared = q

The number of children sharing the money = 8

The relation is division(/)

the amount of money to be shared(q) / the number of children sharing the money(8)

Algebraic sentence:
q /8

PUSH IT IN!

Go over the examples again. Write the mathematical statements down in your note pad and attempt writing them as algebraic sentence without looking at the examples.

 Did you get them? 

Yes? Good! Now go to the activity

.

No? That’s ok! Go over the examples again and try to push it in.

You still did not get it? Good! Send me a COMMENT. There are some little misunderstandings here. Let’s solve it together. I’m expecting your COMMENT! 

   

ACTIVITY

Write the algebraic sentence to the following mathematical statements. Use the method in the examples above.

1.  Anna’s pocket money was increased by $8 today. What is Anna’s new pocket money?
2.  Wao! Steven’s weight reduction program is working, he lost 8 pounds. Imagine Steven’s weight now
3. My father is 3 times older than I am. What is my father’s age?
4. A chicken laid some number of eggs in 5 days, what is the average number of egg laid per day?

Post the solution as a COMMENT to this lesson. Your COMMENT will be replied, include your name or nickname and email. I’m expecting your COMMENT.

 
Congratulation! You've completed this lesson. Now let's go to LESSON 3: OPEN SENTENCE.