Sami lights up a candle every 10 minutes. Every candle burns for exactly 40 minutes. How many candles are burning exactly 55 minutes after Sami lit up the first candle?

4

Step-by-step explanation:

Candle is lit every 10 minutes :

Number of candles lit in 55 minutes:

Starting from 0 minute ; Numbe rod candles lit on 55 minutes = 6

1st candle burns out after 40 minutes

Second burns out after 50 minutes

Third will burn out after 60 minutes

Hence Number of candles still burning :

Number of candles lit - Number of candle burnt out

6 - 2 = 4 candles

geometry: triangles

solvers

lessons

answers archive

call the larger triangle abc

then the smaller triangle cde is similar to abc (all angles are equal, aaa).  

ab is the side that is 36, and we wish to find de, the side corresponding to ab

area_cde = area_abc - area_cde --> area_abc / area_cde = 2

let x=length of de

ratio of areas = (ratio of sides)^2

+2+=+%2836%2fx%29%5e2+

+2+=+1296%2fx%5e2+

++x%5e2+=+1296%2f2+=+648+

25.45584