The Everton College Store Paid $1660 For An Order Of 44 Calculators. The Store Paid $11 For Each Scientific Calculator. The Others, All Graphing Calculators, Cost The Store $53 Each. How Many Calculator Was Order For Each?

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1. Let S be the number of scientific calculators, G be the number of graphing calculators.  S + G = 44    (the store bought 44 calculators)  11S + 53G = 1660    (the total purchase was $1660)    Multiply the first equation by 11 and subtract from the second  (11S+53G) - 11(S+G)  = (1660) - 11(44)  42G = 1176  G = 1176/42 = 28  S = 44-28 = 16  The store ordered 16 scientific and 28 graphing calculators.    2. Use the elimination methd  .3x - .2y = 4  .2x + .3y = -23/19  Multiply the first equation by 3 and add to 2 times the second equation. This will eliminate y.  3(.3x-.2y) + 2(.2x+.3y) = 3(4) + 2(-23/19)  .9x + .4x = 12 - 46/19  1.3x = (228-46)/19  x = 182/(19*1.3) ≈ 7.3684  y = (.3x-4)/.2 = 1.5x-20 ≈ 1.5(7.3684)-20 = -8.9474    3. Use the elimination method  .05x + .25y = 66  .15x + .05y = 72  Multiply the first equation by 3 and subtract the second. This will eliminate x.  3(.05x+.25y) - (.15x+.05y) = 3(66) - 72  .75y - .05y = 198-72  y = 126/.70 = 180  x = (66-.25y)/.05 = 21/.05 = 420  Check: .15(420)+.05(180) = 63+9 = 72    4. P = 190 = 2(w+(w+29))  95 = 2w + 29  66 = 2w  33 inches = width  62 inches = length

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