![\"\"](\"https:\/\/teachmelife.b-cdn.net\/wp-content\/uploads\/2026\/09\/20a1a2d92d2d0d3e0bf1e0c7eb04355f.png\")
<\/p>\n
At first glance, it looks like a trick from a math test.<\/p>\n
The challenge asks you to find a missing angle marked with a red question mark.<\/p>\n
It even adds a bold rule at the top: \u201cNo pen! No paper!!\u201d<\/p>\n
This means you have to solve the whole puzzle using only your mind.<\/p>\n
Let us walk through the steps together to find the correct answer easily.<\/p>\n
First, let us look carefully at the drawing on the page.<\/p>\n
We have a horizontal line at the bottom that forms the base.<\/p>\n
There is a straight line going up to the left, forming an angle of 100 degrees on the outside left.<\/p>\n
There is another line sloping down to the right, forming an angle of 160 degrees on the outside right.<\/p>\n
These two sloping lines meet each other inside to form a triangle.<\/p>\n
Our goal is to find the angle at the top corner inside that triangle.<\/p>\n
To solve this, we need to remember one basic rule about straight lines.<\/p>\n
A completely straight line always forms an angle of 180 degrees.<\/p>\n
When a line is divided into two parts, those two parts must add up to 180 degrees.<\/p>\n
Let us find the bottom-left inside angle of the triangle first.<\/p>\n
The outside angle on the left is 100 degrees.<\/p>\n
Since the total angle on that straight line is 180 degrees, we subtract 100 from 180.<\/p>\n
180\u00b0 \u2013 100\u00b0 = 80\u00b0<\/p>\n
So, the bottom-left inside angle of the triangle is 80 degrees.<\/p>\n
Now, let us find the bottom-right inside angle of the triangle.<\/p>\n
The outside angle on the right side is 160 degrees.<\/p>\n
Using the same straight line rule, we subtract 160 from 180.<\/p>\n
180\u00b0 \u2013 160\u00b0 = 20\u00b0<\/p>\n
So, the bottom-right inside angle of the triangle is 20 degrees.<\/p>\n
Next, we look at the shape formed inside by the three lines.<\/p>\n
It is a simple triangle with three corners.<\/p>\n
Another key rule in geometry is that all three inside angles of any triangle always add up to 180 degrees.<\/p>\n
We already know two of these inside angles: 80 degrees and 20 degrees.<\/p>\n
Let us add these two angles together.<\/p>\n
80\u00b0 + 20\u00b0 = 100\u00b0<\/p>\n
Now, to find the third inside angle at the top, we subtract 100 from 180.<\/p>\n
180\u00b0 \u2013 100\u00b0 = 80\u00b0<\/p>\n
This means the top inside angle of the triangle is 80 degrees.<\/p>\n
Finally, we are ready to find the missing angle with the red question mark.<\/p>\n
Look closely at the top corner where the red arc is drawn.<\/p>\n
The line passing through that corner is a single straight line.<\/p>\n
The top inside angle of the triangle and the missing angle sit right next to each other on this straight line.<\/p>\n
Together, they must add up to 180 degrees.<\/p>\n
Since the top inside angle is 80 degrees, we subtract 80 from 180 to get the missing angle.<\/p>\n
180\u00b0 \u2013 80\u00b0 = 100\u00b0<\/p>\n
The missing angle marked with the red question mark is exactly 100 degrees!<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"