WRITING AND EVALUATING EXPRESSIONS
About "Writing and evaluating expressions"
"Writing and evaluating expressions" is one of the important basic stuff of algebra in math.
Students who would like to learn solving word problems in math must study this basic stuff.
Writing expressions for the given verbal phrases
Let us see, how to write verbal phrase into expressions.
If there is any unknown value, in the given verbal phrase, replace it by some English alphabet.
Example 1
Example 2
Example 3
Writing expressions - Practice questions
To have better understanding on "writing expressions", let us look at some practice questions.
Question 1 :
Write the given verbal phrase into mathematical expression
"The sum of 5 times a number and 8"
Answer :
5x + 8
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Question 2 :
Write the given verbal phrase into mathematical expression
"2 times the sum of 7 times a number and 4"
Answer :
2(7x + 4)
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Question 3 :
Write the given verbal phrase into mathematical expression
"7 less than 4 times a number"
Answer :
4x - 7
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Question 4 :
Write the given verbal phrase into mathematical expression
"One fifth of sum of 3 times a number and 9"
Answer :
( 3x + 9 ) / 5
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Question 5 :
Write the given verbal phrase into mathematical expression
"One seventh of 3 less than 4 times a number"
Answer :
( 4x - 3 ) / 7
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Question 6 :
Write the given verbal phrase into mathematical expression
"5 times of a number is decreased by 8"
Answer :
5x - 8
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Question 7 :
Write the given verbal phrase into mathematical expression
"6 times of a number is increased by 15"
Answer :
6x + 15
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Question 8 :
Write the given verbal phrase into mathematical expression
"7 less than 3 times the sum of a number and 6"
Answer :
3(x + 6) - 7
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Question 9 :
Write the given verbal phrase into mathematical expression
"3 times the difference between a number and 8"
Answer :
3(x - 8)
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Question 10 :
Write the given verbal phrase into mathematical expression
"One fourth of 3 times the difference between a number and 6"
Answer :
3(x - 6) / 4
Evaluating expressions - Practice questions
To have better understanding on "evaluating expressions", let us look at some practice questions.
Question 1 :
Evaluate the given expression for x = 3 and y = 5.
3x + 2y
Answer :
Plug x = 3 and y = 5 in the given expression
3(3) + 2(5) = 9 + 10 = 19
Hence, the answer is 19
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Question 2 :
Evaluate the given expression for m = 5 and n = 2.
m² + 2mn²
Answer :
Plug m = 5 and n = 2 in the given expression
5² + 2(5)(2)² = 25 + 40 = 65
Hence, the answer is 65
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Question 3 :
Evaluate the given expression for s = 5.
s² + 7s - 2
Answer :
Plug s = 5 in the given expression
5² + 7(5) - 2 = 25 + 35 - 2 = 58
Hence, the answer is 58
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Question 4 :
Evaluate the given expression for m = 1/3.
18m² + 3m + 7
Answer :
Plug m = 1/3 in the given expression
18(1/3)² + 3(1/3) + 7 = 2 + 1 + 7 = 10
Hence, the answer is 10
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Question 5 :
Evaluate the given expression for m = 13.
m² + m - 54
Answer :
Plug m = 13 in the given expression
13² + 13 -54 = 169 + 13 - 54 = 128
Hence, the answer is 128
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Question 6 :
Evaluate the given expression for x = 3 and y = 5.
x² + y²
Answer :
Plug x = 3 and y = 5 in the given expression
3² + 5² = 9 + 25 = 34
Hence, the answer is 34
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Question 7 :
Evaluate the given expression for m = 5 and n = 2.
5m² + 2m²n
Answer :
Plug m = 5 and n = 2 in the given expression
5(5)² + 2(5)²(2) = 125 + 100 = 225
Hence, the answer is 225
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Question 8 :
Evaluate the given expression for s = 6.
s² -3s + 10
Answer :
Plug s = 6 in the given expression
6² - 3(6) + 10 = 36 - 18 + 10 = 28
Hence, the answer is 28
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Question 9 :
Evaluate the given expression for x = 2 and y = -5.
x² - 3y²
Answer :
Plug x = 2 and y = -5 in the given expression
2² + 3(-5)² = 4 + 75 = 79
Hence, the answer is 79
Let us look at the next question on "Evaluating expressions"
Question 10 :
Evaluate the given expression for m = 3.
(2m² + 5m - 7) / 2
Answer :
Plug m = 3 in the given expression
[2(3)² + 5(3) - 7] / 2 = [18 + 15 - 7 ] / 2 = 26 / 2 = 13
Hence, the answer is 13
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