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Help me with Pythagorus' Theorem

I put up a post a few minutes ago saying how I'm studying early as I'm aiming for a B in my Maths GCSE. Well,at the moment I'm studying Pythagorus' Theorem and I'm stuck on one question. I've tried it three different times and I still can't do it.

It's hard for me to explain but I'll try:
It's the one where two triangles are stuck together,so it looks like one triangle with a line down the middle. Both the longer sides on each of the triangles put together re 6cm and down the middle which is the line connecting them both and would be the shortest side of the triangle if they weren't attached is 4cm. I''m trying to find the length of the long line at the bottom which is c. So I tried figuring out just one triangle and then doubling it because both sides are 6cm but I got the answer 6.3cm and it's supposed to be 8.9. Originally I got 4.5 on my first go. I have to find the length of C and then give the answer to one decimal place but I can't do these types of triangles please help.
Original post by Student-Dancer
I put up a post a few minutes ago saying how I'm studying early as I'm aiming for a B in my Maths GCSE. Well,at the moment I'm studying Pythagorus' Theorem and I'm stuck on one question. I've tried it three different times and I still can't do it.

It's hard for me to explain but I'll try:
It's the one where two triangles are stuck together,so it looks like one triangle with a line down the middle. Both the longer sides on each of the triangles put together re 6cm and down the middle which is the line connecting them both and would be the shortest side of the triangle if they weren't attached is 4cm. I''m trying to find the length of the long line at the bottom which is c. So I tried figuring out just one triangle and then doubling it because both sides are 6cm but I got the answer 6.3cm and it's supposed to be 8.9. Originally I got 4.5 on my first go. I have to find the length of C and then give the answer to one decimal place but I can't do these types of triangles please help.


An image of the question may help more :redface:
Your method is correct, but you seem to have gotten the wrong number out of it.

And if you did get something and rounded it to 4.5, then you should have doubled it.

Edit: I see that this is in GCSEs, please post in the Maths forum next time :smile:
(edited 8 years ago)
Original post by Student-Dancer
I put up a post a few minutes ago saying how I'm studying early as I'm aiming for a B in my Maths GCSE. Well,at the moment I'm studying Pythagorus' Theorem and I'm stuck on one question. I've tried it three different times and I still can't do it.

It's hard for me to explain but I'll try:
It's the one where two triangles are stuck together,so it looks like one triangle with a line down the middle. Both the longer sides on each of the triangles put together re 6cm and down the middle which is the line connecting them both and would be the shortest side of the triangle if they weren't attached is 4cm. I''m trying to find the length of the long line at the bottom which is c. So I tried figuring out just one triangle and then doubling it because both sides are 6cm but I got the answer 6.3cm and it's supposed to be 8.9. Originally I got 4.5 on my first go. I have to find the length of C and then give the answer to one decimal place but I can't do these types of triangles please help.


Remember that in a^2 + b^2 = c^2, the c value is the longest side (hypotenuse, as it is opposite to the right angle). In your triangle, what you call c is actually one of the shorter sides, so instead of adding the squares of 6 and 4 together, you subtract one from the other.

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