**Evaluating real world expressions :**

An algebraic expression is an expression that contains one or more variables and may also contain operation symbols, such as + or -

We can solve many real world problems by evaluating algebraic expressions.

**Example 1 : **

A scientist measures the air temperature in Death Valley, California, and records 50 °C. The expression 1.8c + 32 gives the temperature in degrees Fahrenheit for a given temperature in degrees Celsius c. Find the temperature in degrees Fahrenheit that is equivalent to 50 °C.

**Solution :**** **

**Step 1 :**

Fromm the given information, we have

c = 50 °C

**Step 2 :**

Plug the value into the expression.

1.8c + 32

Plug 50 for c

1.8(50) + 32

Multiply

90 + 32

Add

122

Hence, 122 °F is equivalent to 50 °C.

**Example 2 : **

The expression 6x² gives the surface area of a cube, where x is the length of one side of the cube. Find the surface area of a cube with a side length of 2 meters.

**Solution :**** **

**Step 1 :**

Fromm the given information, we have

x = 2

**Step 2 :**

Plug the value into the expression which represents surface area of the cube.

6x²

Plug 2 for x

6(2)²

Evaluate exponents

6(4)

Multiply

24

Hence, the surface area of the cube 24 m²

**Example 3 : **

The expression x³ gives the volume of a cube, where x is the length of one side of the cube. Find the volume of a cube with a side length of 2 meters.

**Solution :**** **

**Step 1 :**

Fromm the given information, we have

x = 2

**Step 2 :**

Plug the value into the expression.

x³

Plug 2 for x

(2)³

Evaluate exponents

8

Hence, the volume of the cube 8 m³

**Example 4 : **

The expression 60m gives the number of seconds in m minutes. How many seconds are there in 7 minutes?

**Solution :**** **

**Step 1 :**

Fromm the given information, we have

m = 7

**Step 2 :**

Plug the value into the expression.

60m

Plug 7 for m

60(7)

Multiply

420

Hence, there are 420 seconds in 7 minutes.

After having gone through the stuff given above, we hope that the students would have understood "How to evaluate real world expressions".

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