Help me with math!

June 29, 2006 3:10 AM

Please help answer a simple math question.

My apologies for the simpleness of this question, but my math skills, terrible at the best of times, have abandoned me due to the whisky. If the ratio in a street directory is 1:26 000, how many kilometres is 14cm? (please show working: I want to figure it out for myself next time)

posted by azuma to grab bag (5 comments total)

14cm*26000 = 3.64 kilometers
posted by null terminated at 3:13 AM on June 29, 2006

You may want a simpler explanation:

1/26000 = 14cm/x

x = 26000*14cm = 364,000cm

364,000cm * (1m/100cm) * (1km/1000m) = 3.64km
posted by null terminated at 3:23 AM on June 29, 2006

Put the way I worked it out in my head:

14cm is .14 metres

.14 metres on the map is .14m * 26,000 in real life

1000 metres in a kilometre, so thats .14km * 26

You multiply that all the way out, but I figured that .14 is about 1/7, and so we get 26/7, which is 3 and 5/7, which is about 3 and 2/3, and so 3.66km. Pretty close for an approximation.
posted by outlier at 5:00 AM on June 29, 2006

Think of it this way:
Things in the real world are 26 000 times bigger than things on the map.
posted by weapons-grade pandemonium at 9:12 AM on June 29, 2006

The first post is a tad misleading, methinks.

I've got to do it the visual way, and the first post eliminates an implied step that is useless in this example but applies to other cases where one of the numbers isn't 1.

In another situation, such as, "if 2 inches = 33 miles, how much is 7 inches?" Line up the figures as so:



Multiply crossways (7 x 33 = 231) then divide by the only number remaining unused, 2. (231 / 2 = 115.5) That makes 115.5 (miles).

The first post multiplied crossways but didn't divide by 1 because anything divided by 1 is the same number.

For conversions, you can just type "115.5 miles to feet" into google and it'll tell you what it it is.
posted by vanoakenfold at 11:40 AM on June 29, 2006