Answer:
25
Step-by-step explanation:
20^2 + 15^ = c^2
400 + 225 = c^2
625 = c^2
25 = c
Answer
According to newton law of cooling

and

now At Ta = 100
T₀ = 10 °C
T₁ = 12° C

10 = C + 100
C = -90
now,



at time equal to t
T(t) = 70



t = 48.88 s
hence, after 48.88 s the temperature of the body will be 70°C
b) time taken to reach 98°C



t = 390 s
hence, after 390 s the temperature of the body will be 98°C
Price of DVD player ≥ $150
Saved = $80
Amount needed = $150 - $80 = $70
Saving per week = $10
Let x be the number of weeks needed:
80 + 10x ≥ 150
10x ≥ 150 - 80
10x ≥ 70
x ≥ 70 ÷ 10
x ≥ 7
Answer: She needs to save for for at least 7 weeks.
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❖ 4,860 ÷ 10² = 48.6
Convert 10² into a whole number:
10 × 10 = 100
Divide:
4,860 ÷ 10 = 48.6
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