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2 years ago

A two way table shows information about pupils in a primary school

Mathematics

1 answer:

arlik [135]2 years ago

7 0

Answer:

42 boys can count (given)

P(boy & can count) = 0.35

Step-by-step explanation:

P(boy who can count) = 42/120

7/20 = 0.35

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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 $Q(12) = 0.5Q(0)$

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

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

$e^{-12r} = 0.5$

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

$-12r = \ln{0.5}$

$12r = -\ln{0.5}$

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

$r = 0.05776$

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

Y= (x-1)^2 + 2 change this equation into standard form

BaLLatris [955]

Answer:

x² - 2x + 3

Step-by-step explanation:

y = (x - 1)² + 2

= (x - 1)² + 2 [a - b]² = a²- 2ab + b²

= x²- 2x + 1 + 2

= x² - 2x + 3

Thus, the standard form of the equation is x² - 2x + 3

8 0

2 years ago

Sooo my sis need this so plz help

Morgarella [4.7K]

Answer:

A. They are both Solutions

Step-by-step explanation:

5 0

2 years ago

Read 2 more answers

(っ◕‿◕)っ Please help Asap, Tysm!

storchak [24]

Answer:

40.8

Step-by-step explanation:

When you divide 350 by 51 you get 6.8. Multiply that by 6 you get 40.8

8 0

2 years ago

If f(x)=3x^2 +1 and g(x)=1-x, what is the value of (f-g)(2)

liraira [26]

$(f-g)(x)=3x^2+1-(1-x)=3x^2+1-1+x=3x^2+x\\\\ (f-g)(2)=3\cdot2^2+2=14$

5 0

2 years ago