Sebuah televisi berukuran 24in harus dihubungkan ke sumbertegangan 220V agar dihasilkan daya 68W. Jika televisi tersebut dinyalakan selama 2 jam, maka konsumsi energi televisi dalam seminggu (7 hari) adalah…

1. Sebuah televisi berukuran 24in harus dihubungkan ke sumbertegangan 220V agar dihasilkan daya 68W. Jika televisi tersebut dinyalakan selama 2 jam, maka konsumsi energi televisi dalam seminggu (7 hari) adalah…

diket :
V =220 v
P = 68 w
t  = 2 jam . 7 hr = 14 jam 
dit :Energi listrik
jwb :
W = P . t
W = 68 . 14
W = 952 wh = 0,952 kwh

2. Plywood is sold at Walls-are-Us in 48 in. x 96 in. rectangular sheets. A large job at a local construction site requires the following: 100 36in. x 48in. pieces 200 24in. x 35in. pieces 50 20in. x 48in. pieces 100 16in. x 30in. pieces How many standard sheets of ply wood should be purchased to minimize the cost to the contractor, assuming any cutting patterns are feasible and cutting is free of cost?

1 sheet of plywood, 48*96 = 4608 in. squared

Various plywoord needed
100x sheets (I) of 36*48=1728 in. squared
200x sheets (II) of 24*35=840 in. squared
50x sheets (III) of 20*48=960 in. squared
100x sheets of (IV) 16*30=480 in. squared
In a nutshell we need [tex] \frac{172800+168000+48000+48000}{4608} = 94,791... [/tex] sheets of plywood minimum.

We can easily cut single sheet of 48*96 into 48*40 and 48*56 thus buying 50 sheets of plywood give us, 48*40*50 and giving us 50 sheets of (I) and (III) each. Leftover plywood is 50 sheets of 48*40 in. ,theres 2 option here, we can use leftover for sheets (I) or sheets (III) & (IV), by judging the area, its better to use leftover for sheets (I) instead. Therefore 50 sheets of 48*40 cut into 50 sheets of (I) 48*36 and another leftover is 50 of 48*4 which can't be used anymore.

So far, we got
100x sheets of (I) 48*36
50x sheets of (III) 48*20
By using 50 sheets of plywood.

For sheets of (II) 24*35 and sheets of (IV) 16*30 need to be optimised for 48*96 sheet of plywood.
Two (II) 24*35 left us 48*61 plywood, and by adding Six (IV) 16*30 left us 48*1 plywood.
Therefore single plywood of 48*96 can give us 2 (II) and 6 (IV), we need 16 sheets of plywood to give us 32 (II) and 96 (IV), for last single additional plywood 48*96 we cut it into 4 (IV) 16*30 which can be arranged into 48*30 + 16*30 left us 48*66 - 16*30 for sheets (II) which can be cut into 1 sheets of (II)

So far,
100x sheets of (I)
33x sheets of (II)
50x sheets of (III)
100x sheets of (IV)
By using 67 sheets of plywood.

For last, single plywood of 48*96 give us 4 sheets of (II) 24*35, we need 167 sheets of (II), which needed 42 sheets of plywood.

Therefore total of plywood 109 sheets.