Lesson Worksheet: Multiplying Complex Numbers Mathematics • 12th Grade

In this worksheet, we will practice multiplying two complex numbers.

Q1:

If 𝑟=5+2𝑖 and 𝑠=82𝑖, find 2𝑟+3𝑠.

  • A342𝑖
  • B34+2𝑖
  • C34+2𝑖
  • D14+10𝑖
  • E1+10𝑖

Q2:

What is 7𝑖(5+5𝑖)?

  • A3535𝑖
  • B3535𝑖
  • C35+35𝑖
  • D35+35𝑖

Q3:

Multiply (3+𝑖) by (2+5𝑖).

  • A6+5𝑖
  • B618𝑖
  • C113𝑖
  • D68𝑖
  • E1113𝑖

Q4:

Simplify (118𝑖)(11+8𝑖)+(136𝑖)(13+6𝑖).

Q5:

If 𝑟=2+4𝑖 and 𝑠=8𝑖, find (𝑟𝑠).

  • A75100𝑖
  • B100+25𝑖
  • C125100𝑖
  • D75
  • E10075𝑖

Q6:

Find Re(72𝑖).

Q7:

Simplify (36𝑖)(2𝑖).

  • A15𝑖
  • B2537𝑖
  • C811𝑖
  • D9045𝑖
  • E2736𝑖

Q8:

If 𝑟=2+𝑖, express 𝑟 in the form 𝑎+𝑏𝑖.

  • A6+7𝑖
  • B2+11𝑖
  • C8+𝑖
  • D112𝑖
  • E8𝑖

Q9:

Find the value of 𝑏 such that the complex number (3+4𝑖)(4+𝑏𝑖) is purely imaginary.

Q10:

Solve the equation 𝑖𝑧=4+3𝑖.

  • A𝑧=4+3𝑖
  • B𝑧=34𝑖
  • C𝑧=3+4𝑖
  • D𝑧=3+4𝑖
  • E𝑧=34𝑖

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