Which expression is equivalent to 21 × 7?

Mathematics

1 answer:

Sergio039 [100]3 years ago

6 0

Answer:

Step-by-step explanation:

its the same thing if you multiply 3×4 and 4×3 for example

and you get the same result both times

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A helicopter is at a cruising height of 1,200 feet. Suppose the angle of depression to the landing pad is 15°, which is located

likoan [24]

Answer:

we have a right triangle and to get the internal angle of the right triangle formed at the helicopter we subtract 62 degrees from 90 which equals 28 degrees

we now use the cosine to find the distance (d) from the helicopter

cosine 28 = 85/d

d = 85 / cosine 28 = 85 / 0.8829 = 96.2736 = 96 feet

5 0

3 years ago

the base of a cone has a radius of 6 centimeters. the cone is 7 cenimeters tall. what is the volume of the cone to the nearest t

HACTEHA [7]

Answer:

263.9 cm^3 to nearest tenth.

Step-by-step explanation:

V = 1/3 π r^2 h

= 1/3 π 6^2 7

= 12 * 7 π

= 84π

= 263.8938

4 0

3 years ago

A 20-volt electromotive force is applied to an LR-series circuit in which the inductance is 0.1 henry and the resistance is 30 o

Dafna1 [17]

Answer:

$i(t)=(2/3)(1-e^{-300t})$

Step-by-step explanation:

Before we even begin it would be very helpful to draw out a simple layout of the circuit. Then we go ahead and apply kirchoffs second law(sum of voltages around a loop must be zero) on the circuit and we obtain the following differential equation,

$-V +Ldi/dt+Ri=0$

where V is the electromotive force applied to the LR series circuit, Ldi/dt is the voltage drop across the inductor and Ri is the voltage drop across the resistor. we can re write the equation as,

$di/dt+Ri/L=V/L$

Then we first solve for the homogeneous part given by,

$di/dt+Ri/L=0$

we obtain,

$i(t)_{h} =I_{max}e^{-Rt/L}$

This is only the solution to the homogeneous part, The final solution would be given by,

$i(t)=i(t)_{h} +c$

where c is some constant, we added this because the right side of the primary differential equation has a constant term given by V/R. We put this in the main differential equation and obtain the value of c as c=V/R by comparing the constants on both sides.if we put in our initial condition of i(0)=0, we obtain $I_{max} =V/R$ , so the overall equation becomes,