Sarah performs an experiment to determine the effect of nitrogen on plants. she studies the effect of nitrogen on the growth of the root of hair, height of the plants, and nodule formation. which factor is an independent variable ?

Nitrogen

Explanation:

An independent variable can be changed, altered or manipulated by the experimenter so as to observe the result of such manipulation on the test variable or experimental variable or dependent variable.

Here, nitrogen is the independent variable. The effect of which can be observed on growth of the roots of hair, height of the plants and nodule formation all these factors are the examples of the dependent variables.        

1. (1.2kw)x(15/60hours) = .3kwh --> a

2. (5kw)x(90/60hours)x(8cents/kwh) = $0.60 --> d

3. microwave --> 1200 watts = (1.2kw)x(6/60hours) = .12kwh

coffee-maker --> 900 watts = (.9kw)x(10/60hours) = .15kwh

therefore, it requires more energy for the coffee-maker to do the same amount of work.

so the answer is a.

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