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Number System · Question 6 of 71

Question 6

EasyOriginal question

A tiled wall has 1 tile in the top row, 3 tiles in the second row, 5 in the third, and so on, with each row having 2 more tiles than the row above. How many tiles are there in the first 15 rows?

Options for question 6

Show the answer and explanation
CorrectNot quiteAnswer D

Correct answer: D

Explanation

  1. The rows hold the first 15 odd numbers: 1, 3, 5, …, 29.

  2. Sum of the first n odd numbers = n2=152=225n^2 = 15^2 = 225.

Worth noting

29 is the number of tiles in the 15th row alone; 196 is 14214^2, one row short; 120 is the sum of 1 to 15, the wrong formula.

Concept
Sum of the first n odd numbers
Typical time
35 s
Your time
—
The rule this testsTypes of numbers
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Ten questions from Number System, at your own pace.

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