23. A board for a shelf is 2.31 m long and 33.4 cm wide. to. What is the area of ​​the shelf in square meters? b. What is the perimeter of the shelf in centimeters? c. Which will reduce the area of ​​the shelf more: (1) cutting 3.4 cm from its width, or (2) cutting 0.31 m from its length?

1 m = 100 cmso 2.5 m = (2.5 * 100) = 250 cm

a = 1st shelf

b = 2nd

c = 3rd

d = 4th

a + b + c + d = 250

b = 2a + 18

c = a - 12

d = a + 4

a + (2a + 18) + (a - 12) + (a + 4) = 250

5a + 10 = 250

5a = 250 - 10

5a = 240

a = 240/5

a = 48 cm <== 1st shelf

b = 2a + 18 = 2(48) + 18 = 114 cm <== 2nd shelf

c = a - 12 = 48 - 12 = 36 cm <== 3rd shelf

d = a + 4 = 48 + 4 = 52 cm <== 4th shelf

so 2nd shelf is 114 cm

the answer to this question is 60 n

the minimum amperage that the current in this wire would have to have so that its weight is completely supported by the magnetic force due to earth's field, assuming that no other forces except gravity act on it