Question

Grayson wrote 1.47 ÷ 7 = 2.1 in her math journal.

Answer 1

Answer:

It is incorrect, the right answer is 0.21

Step-by-step explanation:https:

1) If we multiply 1.47 for 100 up and down, we will have the fraction:

100*$\frac{1.47}{1}$ = $\frac{147}{100}$

2) Now we can use division of fractions, it is easier when solving a problem like that:

$\frac{147}{100}$ ÷ $\frac{7}{1}$ = $\frac{147}{100}$*$\frac{1}{7}$

as we know, when dividing fractions you repeat the first and multiply for de inverse of the second

3) $\frac{147}{100}$*$\frac{1}{7}$ = $\frac{147}{700}$

4) Simplify. Divide up and down for 7.

$\frac{147}{700}$ = $\frac{21}{100}$

5) Dividing the fraction you will find 0.21

Answer 2

1.47 : 7 = 0.21

Further explanation

We will use several strategies to explain why Grayson's thinking is incorrect.

Actually, by doing the reverse test, which is the multiplication operation, the results are incorrect.

$\boxed{ \ 7 \times 2.1 = 14.7 \ not \ 1.47 \ }$

Strategy A

• 1.47 : 7 = ?

$\boxed{ \ \frac{1.47}{7} \times \frac{100}{100} = \frac{147}{700} \ }$

$\boxed{ \ \frac{1.47}{7} = \frac{147}{7} \times \frac{1}{100} \ }$

$\boxed{ \ \frac{1.47}{7} = 21 \times \frac{1}{100} \ }$

$\boxed{ \ \frac{1.47}{7} = \frac{21}{100} \ }$

Thus, $\boxed{ \ 1.47 \div 7 = 0.21 \ }$

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Strategy B

• 1.47 : 7 = ?

Recall $\boxed{ \ 1.4 = 14 \ tenths \ } \ and \ \boxed{ \ 7 \ hundredths = .07 \ }$

$\boxed{ \ 1.47 \div 7 = (14 \ tenths \div 7) + (7 \ hundredths \div 7) \ }$

$\boxed{ \ 1.47 \div 7 = 2 \ tenths + 1 \ hundredths \ }$

$\boxed{ \ 1.47 \div 7 = .2 + .01 \ }$

Thus, $\boxed{ \ 1.47 \div 7 = 0.21 \ }$

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Strategy C

• 1.47 : 7 = ?

$\boxed{ \ 1.47 = 1.4 + .07 \ }$

$\boxed{ \ 1.4 \div 7 = .2 \ }$

$\boxed{ \ .07 \div 7 = .01 \ }$

_________ +

Thus, $\boxed{ \ 1.47 \div 7 = 0.21 \ }$

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Strategy D

• See the attached picture.

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Keywords: Grayson wrote, 1.47 ÷ 7 = 2.1, in her math journal., use words, numbers, or pictures, to explain why, Grayson’s thinking is incorrect, tenths, hundredths