Answer:
(a) 13.85 °C
Step-by-step explanation:
The temperature difference is a decaying exponential function of time. Here, it decreases from an initial difference of 15 °C to 10 °C after 25 minutes. So, that temperature difference can be modeled as ...
ΔT = 15(10/15)^(t/25)
We want to find the value of this at t=55. It is ...
ΔT = 15(2/3)^(55/25) ≈ 6.15
This is the amount the temperature of the drink is below room temperature.
drink temperature = (20 - 6.15) °C = 13.85 °C
The temperature of the drink after 55 minutes is about 13.85 °C.
The amount of the tip is 12%
The change is the remaining money that is needed to take from the seller so a change of Umberto will be $6.62.
<h3>What is subtraction?</h3>
To subtract in mathematics is to take something away from a group or a number of objects.
The group's total number of items decreases or becomes lower when we subtract from it.
Given that,
Umberto buys a game for $7.89 and some batteries for $5.49.
Total money of buying = 7.89 + 5.49 = $13.38
Now he gives a $20 bill.
Remaining (change) = 20 - 13.38
⇒ $6.62
Hence "The change of Umberto will be $6.62".
For more about subtraction,
brainly.com/question/1927340
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