Lesson Worksheet: Inductive Reasoning and Conjecture Mathematics

In this worksheet, we will practice writing a conjecture based on inductive reasoning and finding a counterexample.


The paper sizes in the A series are similar rectangles, where A1 is half of A0, A2 is half of A1, A3 is half of A2, and so on, as shown in the diagram.

Consider any two consecutive sizes in the A series.

Find the value of 𝑎𝑏.

  • A2
  • B2
  • C2
  • D12
  • E12


The figure shows the steps to producing a curve 𝐶. It starts as the boundary of the unit square in Figure (a). In Figure (b), we remove a square quarter of the area of the square in (a). In Figure (c), we add a square quarter of the area that we removed in (b). In Figure (d), we remove a square quarter of the area of the square we added in (c). If we continue to do this indefinitely, we will get the curve 𝐶. We let 𝑅 be the region enclosed by 𝐶. By summing a suitable infinite series, find the area of region 𝑅. Give your answer as a fraction.

  • A56
  • B34
  • C45
  • D15
  • E12


An equilateral triangle has a side length of 14 cm, where another triangle is drawn inside of it by connecting the midpoints of its sides. More interior triangles are to be repeatedly drawn the same way as shown in the figure. Find the sum of the perimeters of the first 6 triangles drawn giving the answer to the nearest integer.


Complete the pattern: ,,75,375,1875,,.

  • A3,15,9375,46875
  • B65,70,1880,1885
  • C3,12,7500,30000
  • D3,9,5625,16875


A rectangle whose length is 64 cm and width is 48 cm has its sides bisected. These points are then connected creating a rhombus. The sides of the rhombus are bisected and so on forming the figure below. Find the sum to infinity of the perimeters of the figure.


Select the counterexample to each of the given statements.

All integers have an even number of distinct factors.

  • A12
  • B3
  • C6
  • D9
  • E15

The expression 2𝑛5𝑛+1 is positive for all values of 𝑛.

  • A1
  • B2
  • C4
  • D2
  • E0


Identify the counterexample to this statement: There is no positive integer other than 6 that is equal to half the sum of its positive divisors.

  • A1
  • B18
  • C28
  • D8
  • E24


Find the tenth term of the sequence 13,13,26,39,65,104,169,.


Hoor is helping her little sister learn the pairs of numbers that add up to 10. She uses Cuisenaire rods to show her the pairs 1–9, 2–8, and so forth, that all add up to 10. Looking at the pattern she has made with the rods, she realizes that it could help her figure out the sum of the numbers between 1 and 9 without adding up all the numbers.

Write the calculation that Hoor made to find 1+2++9.

  • A10×9
  • B8×93
  • C9×9
  • D10×92
  • E9×92


In the figure, each square represents one square unit. Letting 𝑥 be the number of columns in the shape and 𝑦 its area measured in square units, write a formula for the area of the shape in terms of 𝑥. Then, calculate the value of 𝑦 when 𝑥=6.

  • A𝑦=3𝑥+3, 𝑦=21
  • B𝑦=𝑥1, 𝑦=35
  • C𝑥=𝑦1, 𝑦=37
  • D𝑦=4𝑥1, 𝑦=23

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