1. CHAPTER 1.4, DATE_______

2. DIRECT VARIATION 1. Line through the origin 2. y varies directly as x (as x changes so will y at a constant rate, k) y = kx 3. k is called the “constant of variation”

3. Find the constant of variation, k, and the direct variation equation if y varies directly as x and y = -24 when x = 4 1 st plug given into formula and solve for k (y=kx) -24 = k(4) 4 -6 = k 2 nd rewrite equation with the constant (k) y = -6x

4. Find the constant of variation, k, and the direct variation equation if y varies directly as x and y = 5 when x = -0.1 1 st plug given into formula and solve for k (y=kx) 5 = k(-0.1) -0.1 -50 = k 2 nd rewrite equation with the constant (k) y = -50x

5. If the table represents a direct variation, write an equation for the variation. XY 14 28 312 416 520 1 st – divide y by x 2 nd -does it stay consistent? 3 rd -write it in direct variation 4 yes y = 4x

6. If the table represents a direct variation, write an equation for the variation. XY 1-6 -542 -1190 -17138 -23186 1 st – Divide y by x 2 nd -does it stay consistent? 3 rd -write it in direct variation no Can’t

7. Cross Product Property of Proportions a c b d = IF Then ad = bc

8. Solve using the cross product property x + 1 9 5x 40 = w 4 10 12 = 40(x+1) = 45x 12w = 40 12 W = 3.33 Ex 1. Ex 2. 40x + 40 = 45x -40x 40 = 5x 5 x = 8

9. Find the cost of 8 pairs of socks if 3 pairs of socks cost $6.90. 1 st – set up a comparison of the given information. socks $ 2 nd - plug in what you know-staying consistent with tops and bottoms 3 $6.90 8 x = 3 rd – cross multiply and solve. 3x = 55.2 x = $18.40

10. Find the cost of 7 apples if 4 apples cost cost $4.50. 1 st – set up a comparison of the given information. apples $ 2 nd - plug in what you know-staying consistent with tops and bottoms 4 $4.50 7 x = 3 rd – cross multiply and solve. 4x = 31.50 x = $7.88