# Thread: area of a triangle

1. ## area of a triangle

hi, i need to know the area of this shape, what i think i have to do is 7x3=21 then double it to get the answer, am i right? if not please show me how to do this question, thanks

2. Originally Posted by andyboy179
hi, i need to know the area of this shape, what i think i have to do is 7x3=21 then double it to get the answer, am i right? if not please show me how to do this question, thanks

Hi andyboy179,

Remember your formula for the area of a triangle?

$A=\frac{1}{2}bh$

Now, it looks to me like your base (b) is 3 units long and your height (h) is 7 units long.

Just apply the formula.

3. Originally Posted by masters
Hi andyboy179,

Remember your formula for the area of a triangle?

$A=\frac{1}{2}bh$

Now, it looks to me like your base (b) is 3 units long and your height (h) is 7 units long.

Just apply the formula.
so do i do 3x7=21 then 21x2=42, which makes 42 as my answer?

4. Originally Posted by andyboy179
so do i do 3x7=21 then 21x2=42, which makes 42 as my answer?
Why did you do that? How did you come to that? If you look at the formula given to you, it is not telling you to multiply 21 by 2. You multiplied the base by height and you got 21. You are right up to there. So what do you next? You simply divide by 2, that is all the formula was telling you.

5. Originally Posted by andyboy179
so do i do 3x7=21 then 21x2=42, which makes 42 as my answer?
The formula says to multiply the base times the height and then take half of that product to get the area.

base X height = 3 X 7 = 21

1/2 X 21 = 10.5 square units for the area.

As the formula goes....

$A=\frac{1}{2}bh$

$A=\frac{1}{2}(3)(7)$

$A=\frac{1}{2}(21)$

$A=10.5$

6. Originally Posted by Keep
Why did you do that? How did you come to that? If you look at the formula given to you, it is not telling you to multiply 21 by 2. You multiplied the base by height and you got 21. You are right up to there. So what do you next? You simply divide by 2, that is all the formula was telling you.

so when i get at 21 do i do, 21/2 which is 10.5?

7. Originally Posted by andyboy179
so when i get at 21 do i do, 21/2 which is 10.5?
Yeah.