3 years ago

In a group of 60 children there are three times as many boys as girls.how many girls are there

1 answer:

3 0

3 times as many boys as girls, so write it in the ratio 3:1 (Three boys for every one girl)
Add up all the numbers in the ratio (3 + 1 = 4)
Divide the total number of children (60) by the number you just worked out (4)
Multiply the resulting number (60/4 = 15) by the ratio of girls (1)
15 * 1 = 15, there were 15 girls in the class (And so 45 boys)

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A motion sensor has a range of 65 meters as shown. The ultrasonic waves sweeping out from the sensor span an angle of 135°.

VMariaS [17]

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<h3>How to determine the area of the range?</h3>

The figure is not given, however the area of the range can be calculated without the figure.

The given parameters are:

Angle, ⊕ = 135°

Radius, r = 65 meters

The area of the range is calculated using the following sector area

$A = \frac{\theta}{360} * \pi r^2$

This gives

$A = \frac{135}{360} * 3.14 * 65^2$

Evaluate

A = 4974.9375

Approximate

A = 4975

Hence, the approximate area that is within range of the motion sensor is 4975 square meters