Suppose the English could drill the Channel in 6.2 years, then they drill with speed $\dfrac{L}{6.2}$ km per year, where L is the length of the English Channel. If the French could drill in 5.8 years, then their speed of drillling is $\dfrac{L}{5.8}$ km per year.

Together their speed will be

$\dfrac{L}{6.2} +\dfrac{L}{5.8} =\dfrac{5.8L+6.2L}{6.2\cdot 5.8}=\dfrac{12L}{35.96}=\dfrac{3L}{8.99}$ .

If they drill together, they will spend

$\dfrac{L}{\frac{3L}{8.99}} =\dfrac{8.99}{3}=2.9966666....\approx 3$ years.

Answer: it would have taken nearly 3 years.

7 0

3 years ago

Find the possible value or values of y in the quadratic equation z^2 - 4z+ 4 =0

jeyben [28]

Didn't you mean "Find the possible value or values of z? y is not at all present in this equation.

z^2 - 4z + 4 = 0 can be factored into (z-2)(z-2). Thus, the given equation has two equal, real solutions: z=2 and z=-2.

5 0

3 years ago

Given that sin0=21/29 what is the value cos 0 for 0°< 0<90°

sp2606 [1]

Answer:

20/29

Step-by-step explanation:

sin θ = 21/29

Use Pythagorean identity:

sin² θ + cos² θ = 1

(21/29)² + cos² θ = 1

441/841 + cos² θ = 1

cos² θ = 400/841

cos θ = ±20/29

Since 0° < θ < 90°, cos θ > 0. So cos θ = 20/29.

3 0

3 years ago