What is the greatest fraction you can make using the digits 4, 7, and 9?

  (7^9)/4 = 40,353,607/4

Step-by-step explanation:

Assuming each digit is used once and exponentiation is allowed, the largest numerator and smallest denominator will result in the largest fraction.

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If other functions, such as factorial are allowed, then there might need to be a limit on the number of times they are applied. For example,

  (7!)^(9!)/4 has about 1 million digits

something like ...

  ((7!)^(9!))!/4 has many more digits than that

and you can keep piling on the factorial symbols to any desired depth.

-3.5 degrees per hour

step-by-step explanation:

find the unit rate:

-12   1/4 degrees           12.25 degrees

= - = -3.5 degrees per hour

      3   1/2 hours               3.5 hours