2. 11.0294118 liters.

3. 220 kilometers.

4. 216 seconds, or 3 minutes and 36 seconds.

You have too many questions at a time.

I’m answering only one question.

How many seconds are there in 55 years.

1. 1. Minutes= 60 seconds

2. 1. Hour x 60 mins = 3,600 seconds

3. 1. Day. 3,600 x 24 hrs = 86400 seconds

4. 1 Year. 86400 x 365 dys = 31536000 seconds

5. 55 years.31536000 x 55 = 17344800

6. Leap Year. 55/4= 13.75 days

=1 day=86400 seconds x 13.75 dys = 1188000 seconds

1,734,480,000 + 1188000 = 1,853,280,000 seconds

55 years = 1,853,280,000 seconds.

Answer in words:

Fifty five years: 1 Threelion, Eight hundred and fifty three billion, two hundred and eighty thousand million seconds.

So,

55*365*24*60*60 = 3902580000

add to that 13 extra days worth of seconds for leap years so 3902580000 + 13*24*60*60 = 3903703200 seconds total

2) Density = mass / volume

so

0.68 = 7.5 / x

0.68x = 7.5

7.5/0.68 = x

x = 11.03

3) The cyclist does 40 km in one hour, so he does 220 km per hour. Now convert that to meters and you get 220000 meters in 5.5 hr

4) 15 seconds per minute, 60 minutes per hour, 24 hours per day

So

.15*60*24 = 21600 seconds per day

Divide by 60 to get minutes = 360 minutes per day

If there are 14 leap years in the 55 then 1,715,689,600

If there are 13 leap years in the 55 then 1,735,607,200

86,400 seconds in a day

31,536,000 seconds in a year

1,734,480,000 seconds in 55 years (plus several days for leap year)