Let Us Practise 4.4

Set up equations and solve for the unknown number in the following cases:

(i) Add 4 to 5 times a number to get 64.

(ii) Nine less than one-half a number is fourteen.

(iii) Ten decreased by twice a number is two.

(iv) When I subtract 2 from 8 times a number, I get 22.

(v) Sita thinks of a number. If she adds 19 to it and divides the sum by 5, she will get 8.



Answer :

Certainly! Let's set up and solve the equations for each of the given scenarios step-by-step.

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### Part (i): Add 4 to 5 times a number to get 64.

1. Set Up the Equation:
Let the unknown number be [tex]\( x \)[/tex].
The equation is [tex]\( 5x + 4 = 64 \)[/tex].

2. Isolate [tex]\( x \)[/tex]:
Subtract 4 from both sides:
[tex]\[ 5x = 64 - 4 \][/tex]
Simplify the right-hand side:
[tex]\[ 5x = 60 \][/tex]
Divide both sides by 5:
[tex]\[ x = \frac{60}{5} \][/tex]
[tex]\[ x = 12 \][/tex]

So, the number is [tex]\( x = 12 \)[/tex].

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### Part (ii): Nine less than one-half a number is fourteen.

1. Set Up the Equation:
Let the unknown number be [tex]\( x \)[/tex].
The equation is [tex]\( \frac{1}{2}x - 9 = 14 \)[/tex].

2. Isolate [tex]\( x \)[/tex]:
Add 9 to both sides:
[tex]\[ \frac{1}{2}x = 14 + 9 \][/tex]
Simplify the right-hand side:
[tex]\[ \frac{1}{2}x = 23 \][/tex]
Multiply both sides by 2:
[tex]\[ x = 2 \times 23 \][/tex]
[tex]\[ x = 46 \][/tex]

So, the number is [tex]\( x = 46 \)[/tex].

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### Part (iii): Ten decreased by twice a number is two.

1. Set Up the Equation:
Let the unknown number be [tex]\( x \)[/tex].
The equation is [tex]\( 10 - 2x = 2 \)[/tex].

2. Isolate [tex]\( x \)[/tex]:
Subtract 10 from both sides:
[tex]\[ -2x = 2 - 10 \][/tex]
Simplify the right-hand side:
[tex]\[ -2x = -8 \][/tex]
Divide both sides by -2:
[tex]\[ x = \frac{-8}{-2} \][/tex]
[tex]\[ x = 4 \][/tex]

So, the number is [tex]\( x = 4 \)[/tex].

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### Part (iv): When I subtract 2 from 8 times a number, I get 22.

1. Set Up the Equation:
Let the unknown number be [tex]\( x \)[/tex].
The equation is [tex]\( 8x - 2 = 22 \)[/tex].

2. Isolate [tex]\( x \)[/tex]:
Add 2 to both sides:
[tex]\[ 8x = 22 + 2 \][/tex]
Simplify the right-hand side:
[tex]\[ 8x = 24 \][/tex]
Divide both sides by 8:
[tex]\[ x = \frac{24}{8} \][/tex]
[tex]\[ x = 3 \][/tex]

So, the number is [tex]\( x = 3 \)[/tex].

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### Part (v): Sita thinks of a number. If she adds 19 to it and divides the sum by 5, she will get 8.

1. Set Up the Equation:
Let the unknown number be [tex]\( x \)[/tex].
The equation is [tex]\( \frac{x + 19}{5} = 8 \)[/tex].

2. Isolate [tex]\( x \)[/tex]:
Multiply both sides by 5:
[tex]\[ x + 19 = 8 \times 5 \][/tex]
Simplify the right-hand side:
[tex]\[ x + 19 = 40 \][/tex]
Subtract 19 from both sides:
[tex]\[ x = 40 - 19 \][/tex]
[tex]\[ x = 21 \][/tex]

So, the number is [tex]\( x = 21 \)[/tex].

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In summary, the numbers are:
- (i) [tex]\( 12 \)[/tex]
- (ii) [tex]\( 46 \)[/tex]
- (iii) [tex]\( 4 \)[/tex]
- (iv) [tex]\( 3 \)[/tex]
- (v) [tex]\( 21 \)[/tex]

I hope this helps! If you have any more questions, feel free to ask.