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How Can I multiply

x = (0.35)(80)

x = 28
steps by step fastest way

I am not going to lie, but it is time for me to take a test without using a calculator. Schools have made me worse by giving us a calculator in exam. now in GRE exam I can't use it.

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    @J.G. sorry $f$ixed, I am wor$k$ing on so many prob$l$ems.2012-10-17

7 Answers 7

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I would just set it up like a regular multiplication, then apply the two decimals at the end. $\ \ \ 35 \\ \underline{\times \ 80} \\ 2800$ Now apply the two decimals to get $28.00$

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You could for example do $10 \times 0.35 $ then subtract $0.35$. That would be my favourite option. However, it would not give you $20$!$9 \times 0.35=10 \times 0.35 - 0.35= 3.5-0.35 =3.15 $

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    I made a big mistake, it was 80 * .35 = 282012-10-17
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9 x 0.35 is only four steps:

  1. 9 x 5 carrying the four,

  2. 9 x 3 + 4 (add the carried four +1 step)

  3. 0 + 3

enter image description here

Where did you get 20 steps from!

Multiplying Decimals - Khan Academy

EDIT:

80 x 0.35 is actually easier as there is no carrying.. I recommend you watch the Khan Academy video.

enter image description here

Three Steps:

  1. 8x5
  2. 8x3
  3. 4+4
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    @Mogli 80 x .35 is also four steps2012-10-17
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$9 \times 0.35 = 9 \times \frac{35}{100} = \frac{315}{100} = 3.15$

This reduces it to just calculating $9 \times 35$.

IMHO if you are taking the GRE, it is better to convert the decimal to the form $\frac{x}{100}$ and reduce the problem to simple multiplication of the first term and the numerator. Then, dividing by $100$ is easy.

I took the GRE general test recently.

Edit

$80 \times 0.35 = 80 \times \frac{35}{100} = 8 \times \frac{35}{10} = \frac{280}{10}$

Once again, you can simplify the problem to multiplication by the first term and the numerator.

IMHO this is the simplest, least error-prone, and fastest way for GRE questions involving decimals.

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    @trideceth12 - Usually GRE takers trip over multiplying by decimals, and GRE questions take advantage o$f$ that. My approach actually turns many o$f$ those questions trivial. Of course, this advice is specific to the GRE test. I would strongly advise GRE takers not to use the methods in the other answers because the questions are counting on confusing test takers trying to juggle fractions or decimals.2012-10-18
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Multiplying and dividing by 10 is easy: shifting to the right or to the left the digits for instance $.35\times 10=3.5$ and $.35/10=.035$.

Can you add decimal fractions? Then $9\times\,.35 = (10-1)\times\,.35 =3.5 -.35 = 3.50 - 0.35 = 3.15$

Or, you can just multiply it, digit by digit from right to left: $5\times 9=45$, so last digit will be $5$ and carry on $4$ for adding to the next digit. $3\times 9=27$ then add the carried $4$, it is $31$, so this digit is $1$ and $3$ is carried to the next digit to the left, yielding indeed $3.15$: $.35\times 9 = \frac{35}{100}\times 9 =\frac{35\times 9}{100} = \frac{315}{100} $

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$0.35=0.25+0.1=\frac{1}{4}+\frac{1}{10}=\frac{7}{20}$

$9\times \frac{7}{20}=\frac{63}{20}=\frac{60}{20}+\frac{3}{20}=3+\frac{3}{20}=3+3\times\frac{1}{20}= 3+3\times 0.05=3.15$