Find the 5th Term in the Sequence: 10, 20, 40, ...

Question

Look at the sequence below:

10,20,40,?,?,? 10,20,40,\text{?,?,?}

What is the 5th element of the series?

Video Solution

Solution Steps

00:10 Let's find the fifth term in the sequence.
00:13 Notice how each term changes from the one before it.
00:20 Use this pattern to figure out the next terms.
00:24 Now, calculate and replace the numbers.
00:39 And that's how we find the answer to the question.

Step-by-Step Solution

To solve this problem, we need to determine the pattern in the sequence 10,20,40,?,?,? 10, 20, 40, \text{?,?,?} .

The terms of the sequence seem to be generated by multiplying by a common ratio of 2. This is characteristic of a geometric sequence.

The first term a1=10 a_1 = 10 .

The second term is a2=a1×2=10×2=20 a_2 = a_1 \times 2 = 10 \times 2 = 20 .

The third term is a3=a2×2=20×2=40 a_3 = a_2 \times 2 = 20 \times 2 = 40 .

Following the pattern of multiplying by 2, we can determine the next terms:

  • The fourth term a4=a3×2=40×2=80 a_4 = a_3 \times 2 = 40 \times 2 = 80 .
  • The fifth term a5=a4×2=80×2=160 a_5 = a_4 \times 2 = 80 \times 2 = 160 .

Thus, the 5th element of the sequence is 160 160 .

Answer

160 160