Answer:
257 is prime.
Step-by-step explanation:
To evaluate if a number is prime, we just need to evaluate it for the prime numbers that are equal or lesser than the said number's square root.
In this case, √257 = 16.03 so we just need to see if 257 is divisible by <u>2, 3, 5, 7, 11 and 13</u> (the prime numbers that come before 16)
- 257 is odd, so it is not divisible by 2.
- The sum of its digits is 14, therefore, it is not divisible by 3.
- 257 ends in 7, therefore it's not divisible by 5.
- 257/ 7 = 36.71 so it's not divisible by 7.
- 257/ 11 = 23.36 so it's not divisible by 11
- Finally 257 / 13= 19.76 so it's not divisible by 13.
Therefore, 257 is prime.
Answer:
(3,1)
Step-by-step explanation:
Answer:
The height above sea level at <em>B</em> is approximately 1,604.25 m
Step-by-step explanation:
The given length of the mountain railway, AB = 864 m
The angle at which the railway rises to the horizontal, θ = 120°
The elevation of the train above sea level at <em>A</em>, h₁ = 856 m
The height above sea level of the train when it reaches <em>B</em>, h₂, is found as follows;
Change in height across the railway, Δh = AB × sin(θ)
∴ Δh = 864 m × sin(120°) ≈ 748.25 m
Δh = h₂ - h₁
h₂ = Δh + h₁
∴ h₂ ≈ 856 m + 748.25 m = 1,604.25 m
The height above sea level of the train when it reaches <em>B</em> ≈ 1,604.25 m
