Kate's model is correct because 10 times the value of 4 rods, 10(4(10)), is 400. Mel's model represents 4(1)=4, which is incorrect. Kate's model represents 4*100=400, which is correct.
Hope I answered your question!
D. 34 and 56 degrees - when added together equal 90 degrees
2800 ÷ 400
Cross out 2 zeros from both numbers, then you have 28 ÷ 4 = 7
Rearrange to: x^2 + 18x - 25 = 0
Then factorise (I like to do it by completing the square):
(x + 9)^2 -81 -25 = 0
(x + 9)^2 = 106
x + 9 = sqrt(106)
The sol'ns are:
x = -9 + and - sqrt(106)
