A 3 by 3cm grid shows nine 1 by 1 cm squares and uses 24cm of wire. What length would the wire be for a similar 20 by 20cm sqaure

840 cm

Step-by-step explanation:

Given that in the question we have, : 9, 1 cm × 1 cm squares setting a 3 × 3 grid.

Therefore wire required in 3 x 3 grid is

3(3+1) + 3(3+1)

= 3 × 4 + 3 × 4

= 24 I'm

Similarly, the length of the wire required in 20 by 20 grid will be

=> 20(20+1) + 20(20+1)

=> 20 × 21 + 20 × 21

=> 420 + 420

= 840cm

step-by-step explanation:

proportions are fractions that equal to each other. so if two fractions are the same, they are proportional.

let's check the answers to see if they are proportional.

question a is not proportional because you can't turn 1.5/3 to 3/9. if you try to multiply 1.5/3 by 2 or 3, you wont get 3/9. it's impossible to make the fractions the same.

question b is not proportional because you can't turn 22/33 to 4/6. 33 can't go into 6.

question c is proportional because when you multiply 2 and 3 by 71, you would get 142/213, and those fractions equal to each other

question d is proportional because when you divide 14 and 7 by 2, you would end up with 7/3.5, and those fractions equal to each other.