Finding the Common Difference - Arithmetic Progressions

Algebra Level 1

The numbers of red circles in each group in the above diagram form an arithmetic progression. What is the common difference?

6 8 10 12

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4 solutions

Yajat Shamji
Aug 2, 2020

4 × 8 = 32 4 \times 8 = 32

2 × 4 = 8 2 \times 4 = 8

32 8 \frac{32}{8} = 4 × 2 = 8 = 4 \times 2 = \fbox{8}

a = 8, a + 3d = 32. d = (32 - 8)/3 = 24/3 = 8.

Jiya Dani - 1 month, 1 week ago
Brilliant Mathematics Staff
Aug 1, 2020

In the above sequence, the first term is a 1 = 4 × 2 = 8 a_1=4\times 2 =8 and the fourth term is a 4 = 4 × 8 = 32 a_4=4 \times 8 = 32 . Hence, the common difference can be obtained as follows: a 4 = a 1 + 3 d d = a 4 a 1 3 = 32 8 3 = 8. a_4=a_1+3d \implies d=\frac{a_4-a_1}{3}=\frac{32 -8}{3} = 8.

Issac Newton Is
Nov 14, 2020

Information provided by the question : First term : 8 Term = 32 No. of steps from the first term : 4

By explicit formula term = first term + common difference X no. Of steps from initial term. 32 = 8 + d X 4 - 1 32 = 8 + 3 d 32 - 8 = 3 d 24 = 3d 24/3 = d 8 = d. Therefore , the common difference is 8

Mahdi Raza
Aug 16, 2020

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