# Need to find formula

• Feb 28th 2007, 02:05 AM
chhoeuk
Need to find formula
Because tsunamis travel very quickly, warning people of an approaching tsunami can be difficult. In 1998, some mexican scientists developed a new method of measuring earthquakes and predicting tsunamis. Before 1998, it took 20 minutes to determine whether and earthquake would produce a tsunami. With the new technology te task may be completed in 5 minutes. What percentage decreases in time is this ?

Thanks, Chhoeuk:confused: :confused:
• Feb 28th 2007, 04:13 AM
earboth
Quote:

Originally Posted by chhoeuk
Because tsunamis travel very quickly, warning people of an approaching tsunami can be difficult. In 1998, some mexican scientists developed a new method of measuring earthquakes and predicting tsunamis. Before 1998, it took 20 minutes to determine whether and earthquake would produce a tsunami. With the new technology te task may be completed in 5 minutes. What percentage decreases in time is this ?

Thanks, Chhoeuk:confused: :confused:

Hi,

the absolute decrease of time: 15 min

Let p be the percentage you are looking for. Then use the proportion:

15/20 = p/100 ===> p = 75%

EB