ElectricPavlov

First choice

second choice is a capacitor

third choice is a potentiometer (technically a variable resistor.....like a volume control)

fourth choice is a power supply or battey

Each outfit can be paired with 4 choices of shoe

4  x 3 = 12 different pairings  (as long as her shoes match!  Haha)

After 28 years there will 1/2  of  10gm left =   5 gm

    after ANOTHER 28 YEARS there will be 1/2  of 5 gm left =  2.5 gm

.5 = 1 e^-k 28

k =.0247553

? = 10 e^-.0247553 (56)

? = 2.5 gm   

R2 and R3  are in parallel....their effective resistance is    (r2 * r3)/ (r2+r3) = 25/10 = 2.5 ohms

  (they each have the same current through them)

the resistance of the entire circuit is   R4 + 2.5 ohms + R1 = 12.5 ohms

The current in the circuit        V/R = I        12 v/ 12.5 ohms = 960 mA

R2 and R3 split this current    960/2 = 480 mA   (or  .48 A )

Set up a ratio

16 cm is to 128 cm²      as     24 cm is to ? cm²

16/128  =  24 /?       solve for ?

Inversely proportional    means    a = k/b       (directly proprtional would be  a = kb)

4 = k 9    results in k =  4/9

a = 4/9 b     put in b = -72   then calc 'a'

a = 4/9 (-72)       results in a = -32

1/2 + 2/8  =  150/x    solvew for x     (200 minutes)

one 5 gal bucket in 2 minutes =     1/5

one 10 gallon bucket in 8 min  =    2/8

750  = 150 five gallon buckets

Oops....forgot dimensions      cm²

15 x 20

13 x 20

12 x 9

12 x 5

14 x 20      Add 'em up !