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Given that $31 \times 417 = 12927$ , without using a calculator , evaluate

$31 \times 0.417 + 12927/4170 $

I'm stuck at how to solve this ...

First I deal with $12927/4170$

From the given equation ,

$ 310 \times 4170 = 129270 $ Therefore .. $12927/4170 = 310$

Then I'm not sure how to deal with $31 \times 0.417 $

Can I get help ? Thanks in advance !

MPW
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user307640
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  • 31417=12927 does not imply 3104170=129270. You have an extra factor of 10. This is obvious since the product must end with 2 zeroes. – user328442 Sep 28 '16 at 04:13
  • 31x417 = 12927 so 12927/417 =31 so 12927/4170 = 31/10=3.1. 31x0.417 =31x417/1000=12927/1000=12.927.so 12.927+3.1=16.027. – fleablood Sep 28 '16 at 07:17

2 Answers2

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Note 1: You made a little mistake on what you did with your factors of $10$ in

$$\frac{12927}{4170}$$

See if you can figure it out.

Note 2: We know that

$$31\times 0.417 = \frac{1}{1000}\times (31\times 417)$$

Can you take it from there?

Carl Schildkraut
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Observe that:

  • $31\times417=12927\implies\color\red{31\times0.417}=\color\red{12.927}$
  • $31\times417=12927\implies\color\green{12927/4170}=\color\green{3.1}$

Therefore: $\color\red{31\times0.417}+\color\green{12927/4170}=\color\red{12.927}+\color\green{3.1}=16.027$

barak manos
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