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3 years ago

What is -4/5 + 3/20 in simplest form

Mathematics

2 answers:

Helga [31]3 years ago

6 0

-4/5 = -16/20, so the new expression is (-16/20)+(3/20)
then, -16 + 3 is -13, so the solution is -13/20

olga2289 [7]3 years ago

5 0

-4/5 + 3/20 = 3/20 - 4/5

To subtract 2 fractions, they both need to have the same denominator.
Since 5 is one of the divisors of 20, we can just multiply the numerator and denominator of 4/5 by 4.
4/5 = (4*4) / (5*4) = 16/20

P.S. when the denominators of both fractions don't have any relation, you multiply the numerator and denominator of the first fraction by the denominator of the second, and the numerator and denominator of the second by the denominator of the first.

3/20 - 4/5 = 3/20 - 16/20

Now you just subtract the numerators:
3/20 - 16/20 = (3-16)/20 = -13/20

So -4/5 + 3/20 = -13/20

Hope this helps! :)

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Given that,

The number of grams A of a certain radioactive substance present at time, in years

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At t=0, we get

$A=45e^{-0.0045(0)}$ $A=45e^0$

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we get,

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b)To find thehalf-life of this substance

To find t when the substance becames half the amount.

A=45/2

Substitute this we get,

$\frac{45}{2}=45e^{-0.0045(t)}$

$\frac{1}{2}=e^{-0.0045(t)}$

Taking natural logarithm on both sides we get,

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Half-life of this substance is 154.02

c) To find the amount of substance will be present around in 2500 years

Put t=2500

we get,