# What is the missing number in this sequence : 1 ,5 , 17 , ? , 79 , 161

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by irajkrasalon

2016-04-05T14:48:19+05:30
Solving Equations
Solving equations is the very beginning of being able to do algebra. Solving equations usually starts in a primary grade, like 1st, 2nd, or 3rd and goes through high school. The basic idea behind solving equations is to be able to find the missing number. In this section, we’re going to start out with the very basics of solving equations, and move on to some harder stuff.

Find the Missing Number
The first major step is to be able to find a missing number. This means that you need to be familiar with your addition, subtraction, multiplication, and division facts. Try a few of the following:

There are two different ways to think about this; you should go with whichever one comes more naturally. You can either start at 5 and count up to 8—the amount you count up is your answer, or, you can subtract 8 – 5, and that number is your answer.

In detail—the first method would involve counting up. That means you start with 5. You’re counting up to 8. So, you already have 5, you say “6, 7, 8.” Three numbers, so your answer is 3.

The second method, in detail, would involve subtraction. You would take the number after the equals sign (8) and subtract the number before the equals sign (5) in order to get 3.

When you first saw the problem, you probably thought of the answer right away in your head, and if you stop and think about it, chances are you used one of the above listed methods. Whichever way came to you first is the way you’ll want to think about it!

Let's try another one: