Question

Justin is evaluating the expression 12.5 + 3.8 x, when x is 7.9.

12.5 + 3.8 (7.9). 16.3 (7.9). 128.77.

What was Justin’s error?

Answer 1

The given expression:

12.5 + 3.8x

We have to find the Justin's error.

Solution:

∴ 12.5 + 3.8x

Put x = 7.9 in the above equation, we get

= 12.5 + 3.8(7.9)

= 12.5 + 3.8(7.9)

= 12.5 + 30.02

= 42.52

Thus, the Justin’s error was second step.

Answer 2

SOLUTION

TO DETERMINE

Justin’s error in is evaluating the expression

12.5 + 3.8 x, when x is 7.9.

12.5 + 3.8 (7.9)

16.3 (7.9)

128.77

EVALUATION

First we write the steps as Justin evaluates

$\sf{12.5 + 3.8x} \: \: when \: \: x = 7.9$

$= \sf{12.5 + 3.8 \times 7.9}$

$= \sf{16.3 \times 7.9}$

$\sf{ = 128.77}$

CORRECT EVALUATION

STEP : 1

$\sf{12.5 + 3.8x} \: \: when \: \: x = 7.9$

STEP : 2

$= \sf{12.5 + 3.8 \times 7.9} \:$

STEP : 3

$= \sf{12.5 + 30.02} \:$

Justin has made a mistake in this step

Justin has not follow the BODMAS rule

Justin has added 12.5 and 3.8 instead of multiplying 3.8 and 7.9

We further proceed for correct answer in the below step

STEP : 4

$= \sf{12.5 + 30.02} \:$

$= \sf{42.52} \:$

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