Answer:
n = 18 cycles
Step-by-step explanation:
To know how many times does the current oscillates in the given time, you take into account that the number of oscillation can be calculated by using the following expression:
(1)
f: frequency of the oscillation of the current
t: time = 0.30s
The frequency is the number of cycles per second, that is, f = 60 cycles/s
You replace the values of f and t in the equation (1):

In 0.30s the current oscillates 18 times
Answer: a) -27, b) 35, c) 14
Step-by-step explanation:
a) When a positive number is multiplied by a negative number, your answer is negative, and since we know that 9 × 3 = 27, and that this figure has to be negative (since 9 is negative), the answer is -27.
b) Multiplying two negative numbers gives a positive number, and since 7 × 5 = 35, the answer is positive 35 (as both 7 and 5 in the original question are negative).
c) Follows just like b.