Marc is half as old as Tony and three times as old as Ben. If the sum of their ages is 40, how old is Marc?
1 answer:
Answer:
Marc's age is 12
Step-by-step explanation:
Let
x ----> Marc's age
y ---> Tony's age
z ---> Ben's age
we know that
the sum of their ages is 40
so
-----> equation A
Marc is half as old as Tony
so
----> equation B
Marc is three times as old as Ben
so
----> equation C
substitute equation B and equation C in equation A
solve for x
therefore
Marc's age is 12
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Answer:
The probability of using one or the other is 36%
Step-by-step explanation:
For solving this problem it is easy if we see it in a ven diagram, for this first we are going to name the initial conditions with some variables:
Probability of passing Professor Jones math class = 64% =0,64
P(J) = 0.64
Probabiliry of passing Professor Smith's physics class = 32% =0.32
P(S) = 0.32
Probability of passing both is = 30% = 0.30
P(JnS) = 0.30 (Is is an intersection so it is in the middle of the ven diagram
We need to know which is the probability of pasing one or the other for this we need to take out the probability of passing both for this we have to add the probability of passing Professor Jones math class with the probabiliry of passing Professor Smith's physics class and substract the probability of passing both for each one:
P(JuS) = (P(J) - P(JnS)) + (P(S) - P(JnS)) = (0.64 - 0.30) + (0.32 - 0.30) = 0.34 + 0.02 = 0.36 = 36%
If you check the ven diagram you can see that if we add all what is in red we will have the probability of passing Professor Jones math class and if we add all what is in blue we wiill have the probability of passing Professor Smith's physics class, and if we add just what is in each corner we will get the same value that is the probabilty of passsing one or the other.
In order to subtract fractions, you need the denominators (bottom number) to be the same. 
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