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Sveta_85 [38]
3 years ago
14

A 20mg sample of thorium-233 decays to 17mg after 5 min. determine the half life of thorium-233?

Mathematics
1 answer:
snow_tiger [21]3 years ago
3 0
Let r be the decay rate (time in minutes) 17 = 20 e^(5r) 0.85 = e^(5r) ln 0.85 = 5r similarly, ln 0.5 = hr ... where h is the half-life, so dividing the 2 equations, ln 0.85 / ln 0.50 = 5r / hr = 5/h h = 5 ln 0.50 / ln 0.85 h = 21.3 min b) 1/20 = 0.05, so ln 0.85 = 5r ln 0.05 = tr t = 5 ln 0.05 / ln 0.85 t = 92.2 min
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A cylindrical roller 2.5 m in length, 1.5 m in radius when rolled on a road was found to cover the area of 16500 m2 . How many r
eduard

Answer:

701 revolutions

Step-by-step explanation:

Given: Length= 2.5 m

            Radius= 1.5 m

            Area covered by roller= 16500 m²

Now, finding the Lateral surface area of cylinder to know area covered by roller in one revolution of cylindrical roller.

Remember; Lateral surface area of an object is the measurement of the area of all sides excluding area of base and its top.

Formula; Lateral surface area of cylinder= 2\pi rh

Considering, π= 3.14

⇒ lateral surface area of cylinder= 2\times 3.14\times 1.5\times 2.5

⇒ lateral surface area of cylinder= 23.55 \ m^{2}

∴ Area covered by cylindrical roller in one revolution is 23.55 m²

Next finding total number of revolution to cover 16500 m² area.

Total number of revolution= \frac{16500}{23.55} = 700.6369 \approx 701

Hence, Cyindrical roller make 701 revolution to cover 16500 m² area.

8 0
3 years ago
Solve this system of linear equation the x- and y-value with a comma. 18x+13y=60 6x+2y=6
OLEGan [10]

Answer:

18x + 13y = 60

6x + 2y = 6 ---> 6x = -2y +6 ---> 18x = -6y+18

Substitution

(-6y +18)+13y =60

       -18           -18

--------------------------

7y = 42 so y=6

Then, 6x + 2(6) =6, which you will get x = -1

(-1, 6)

8 0
2 years ago
Read 2 more answers
PLZ help me with this question
olga2289 [7]

Answer:

3

Step-by-step explanation:

3x4=12

its 3 because you need to find the balances so when you have 3 and you multiped my 4 you get 12 same as the other square.

3 0
2 years ago
What's is the square root of 63
QveST [7]
You want to be finding out what two factors (where one of them is a perfect square) has the produce of 63. It seems like 9 x 7 (9 is the perfect square) works.

\sqrt{63} =  \sqrt{9 \times 7} = \sqrt{9} \times \sqrt{7}

The square root of 9 is 3 so we can just have 3 \sqrt{7} (which just means 3 times the square root of 7). 

3 0
3 years ago
Find a​ point-slope form for the line with slope
Katen [24]

Answer:

It is Third quardant in Graph

7 0
2 years ago
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