## Ruhhr 3 years ago the figures are similar. The area of one figure is given. Find the area of the other figure to the nearest whole number. The area of the large triangle is 177 ft² (will draw figure below) .. A) 100 ft² .. B) 347 ft² .. C) 196 ft² .. D) 90 ft²

1. Ruhhr

|dw:1349190507668:dw| (not drawn to scale)

2. pratu043

What is 14 ft and 10 ft?

3. pratu043

|dw:1349190940501:dw|

4. pratu043

Are you there @Ruhhr?

5. pratu043

?????

6. Ruhhr

Sorry, getting caught up in my work.. & yeah it shows the lenght of the sides... I got that already..

7. pratu043

I'm not really good at this but the ration of the sides are the same right?

8. pratu043

Sorry ratio.

9. pratu043

|dw:1349191230318:dw|

10. Ruhhr

Ratio: is a comparison of two quantities by division.

11. pratu043

So 14:10 = AB:PQ = BC:QR

12. pratu043

14:10 = 7:5

13. Ruhhr

How does it equal 7.5 though? What did you do to get to 7.5?

14. pratu043

No not 7.5 its 7:5. If you divide 14:10 by two, you get 7:5(14/2:10/2). Got that?

15. Ruhhr

Oh yes! Got it! Then what do you do?

16. pratu043

Area of ABC = 177 ft^2 Lets take the base as 14 ft so that we can find the altitude to that base. You need the altitude and the corresponding base to get the area. 1/2 * base * height = 177 1/2 * 14 * h = 177 h = (177 * 2)14 = 25.3 approx. (25.28)

17. pratu043

Pretty straightforward now.

18. pratu043

Got it till here?

19. Ruhhr

wait how did you get 177 when all it provides is 14?

20. pratu043

The area is 177 right? Its given.

21. pratu043

Area of the largest triangle is 177 ft^2.

22. pratu043

sorry larger. Got that?

23. Ruhhr

yes

24. pratu043

So even the heights of the two triangles are in the ratio of 7:5. So lets take the height to the base 10 ft in PQR as x. 25.3:x = 7:5 => 25.3/x = 7/5 Can you find x?

25. Ruhhr

I'm lost @.@

26. pratu043

Lost on how to find x?

27. Ruhhr

yes

28. pratu043

Hint - In the equation 25.3/x = 7/5, cross multiply. You'll get 25.3 * 5 = 7x. Now?

29. Ruhhr

I get 7x = 127.5 by cross multiplying

30. Ruhhr

I get 7x = 127.5 by cross multiplying

31. pratu043

So what's x?

32. Ruhhr

and when i divide that.. i get 18.21

33. Ruhhr

igtg to my next class now

34. pratu043

Yep that's right. So now we have the corresponding base and height for PQR. 1/2 * 18.21 * 10 Easy now?

35. pratu043

You get 91.05. I think you should round off to the nearest ten and write it as 90.