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3 years ago

6

A tank can be filled by three pipes separately in 20,30,and 60 minutes respectively. In how many minutes can it be filled by the

three pipes acting together

1 answer:

vovikov84 [41]3 years ago

5 0

Answer:

Step-by-step explanation:

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Approximately 1,870,000 oz of gold went into the manufacturing of electronic equipment in a certain country in 1 year. This was

Alexxandr [17]

Answer: 17000000 ounces of gold were mined in that country that year.

Step-by-step explanation:

Let x represent the number of ounces of gold that were mined in that country that year.

Approximately 1,870,000 oz of gold went into the manufacturing of electronic equipment in a certain country in 1 year. This was 11% of all the gold mined in that country that year. This means that

11/100 × x = 1870000

0.11x = 1870000

x = 1870000/0.11

x = 17000000

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2 years ago

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Greeley [361]

X is 65 because 65 is great and should always be the answer

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2 years ago

One less than a number, which is then divided by 5, is -7. What is the number?

Paladinen [302]

Answer:

Work backwords.

-7*5=-35

-35-1=-36.

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2 years ago

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3 years ago

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Element X decays radioactively with a half life of 12 minutes. If there are 200 grams of Element X, how long, to the nearest ten

Semenov [28]

Answer:

It would take 24 minutes for the element to decay to 50 grams

Step-by-step explanation:

The equation for the amount of the element present, after t minutes, is:

$Q(t) = Q(0)e^{-rt}$

In which Q(X) decays radioactively with a half life of 12 minutes.(0) is the initial amount and r is the rate it decreases.

Half life of 12 minutes

This means that $Q(12) = 0.5Q(0)$

So

$Q(t) = Q(0)e^{-rt}$

$0.5Q(0) = Q(0)e^{-12r}$

$e^{-12r} = 0.5$

$\ln{e^{-12r}} = \ln{0.5}$

$-12r = \ln{0.5}$

$12r = -\ln{0.5}$

$r = -\frac{\ln{0.5}}{12}$

$r = 0.05776$

If there are 200 grams of Element X, how long, to the nearest tenth of a minute, would it take the element to decay to 50 grams?

This is t when Q(t) = 50. Q(0) = 200.

$Q(t) = Q(0)e^{-rt}$

$50 = 200e^{-0.05776t}$

$e^{-0.05776t} = 0.25$

$\ln{e^{-0.05776t}} = \ln{0.25}$

$-0.05776t = \ln{0.25}$

$0.05776t = -\ln{0.25}$

$t = -\frac{\ln{0.25}}{0.05776}$

$t = 24$

It would take 24 minutes for the element to decay to 50 grams

6 0

3 years ago