In 2004, the world's fastest knitter was able to knit 225 stitches in 3 min. How long would she take to knit a scarf that was 20 cm wide and 1.2 m long, if she used yarn that resulted in 1.6 stitches per centimetre?

Answer: She would take 51 minutes and 12 seconds

Step-by-step explanation: The world's fastest knitter was able to achieve 225 stitches in 3 minutes. This can be broken down into stitches per minute or even per second. For every minute the number of stitches made can be derived as;

Number per minute = Total stitches / Time

Number per minute = 225/3

Number per minute = 75

Also, number per second = 75/60

Number per second = 1.25

The above calculations show that the knitter was able to make exactly 1.25 stitches per second.

She eventually knitted a scarf that was 20 cm by 120 cm (1.2 metres equals 120 centimetres). This means the scarf had a total area of

Area = L x W

Area = 120 x 20

Area = 2400

She also used yarn that resulted in 1.6 stitches per centimetre. The total area of the scarf has been derived as 2400 square centimetres. Therefore the total number of stitches used for the entire scarf is derived as;

Total stitches = Area x stitches per square cm

Total stitches = 2400 x 1.6

Total stitches = 3840

Having earlier calculated her work rate as 1.25 stitches per second, knitting 3840 stitches would take the following amount of time;

Time taken = Total Stitches / Stitch per second

Time taken = 3840/1.25

Time taken = 3072

Therefore she took 3,072 seconds. Converting this into minutes results in (60 seconds equals 1 minute)

Time in minutes = 3072/60

Time in minutes = 51.2 minutes

Also the fraction 0.2 can be converted into the appropriate unit (that is seconds) as follows;

Conversion rate = 0.2 x 60

Conversion rate = 12

Hence the fastest knitter was able to knit a scarf measuring 20 cm by 1.2 m in exactly 51 minutes and 12 seconds