Hwee Bin is a sales executive for a software
company. One-tenth of the cold-calls he makes
can result in a sale. If Hwee Bin makes 3 cold-
calls, find the probability that
(a) the first two cold-calls will result in sales,
(b) there will be no sales,
(c) there will be at least one sale.

the solution of the equation is 2.23 ⇒ answer b

step-by-step explanation:

* lets revise the meaning of exponential function

- the form of the exponential function is y = ab^x, where a ≠ 0, b > 0 ,  

  b ≠ 1, and x is any real number

- it has a constant base b

- it has a variable exponent x

- to solve an exponential equation, take the log or ln of both sides,  

  and solve for the variable

* lets solve the problem

∵

- the base is 7 and the exponent is x

- insert ㏑ in both sides

∴

- use the rule

∴ x ㏑(7) = ㏑(77)

- to find x divide both sides by ㏑(7)

∴

* the solution of the equation is 2.23 to the nearest 2 decimal places

it's undefined because anything multiplied by 0 is 0. that said, 7 days is 168 hours

b is the right answer