It is given that 2^x = 5^y = 10^z , express z in terms of x and y

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  z = (xy)/(x+y)

Step-by-step explanation:

Taking logarithms base 10, we have ...

  x·log(2) = y·log(5) = z·log(10)

  z = x·log(2) = y·log(5) . . . . . . . . log(10) = 1

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Then z/x = log(2), and z/y = log(5), so ...

  z/x +z/y = log(2) +log(5) = log(2·5) = 1

  z = 1/(1/x +1/y) = 1/((x+y)/(xy))

  z = (xy)/(x+y)

Step-by-step explanation:

$53.50

step-by-step explanation:

you have to subtract the amount of money chuck earned ($72.50) by the cost of the gas for the mower ($11.25) and the new string for the trimmer he bought ($7.75).

72.50-11.25=61.25

and then subtract $61.25 by the second thing he bought (the new string for the trimmer)

61.25-7.75=53.5

so in total it's $53.50 (53 dollars and 50 cents)