1. 3.5 Writing Ratios & Proportion
mi/gal ??

2. A RATIO is a quotient
that compare 2 quantities. 3 4
3 : 4
3 to 4

3. A Proportion is an equation of two equal ratios.

4. The numerators have the same units (miles).
The denominators have
the same units (gallons).

5. Proportion is true if fractions are equal when in lowest terms.
all
reduce
to 1/2 = =
Proportion is true if fractions are equal when in lowest terms.

6. Each of the numbers in the proportion is a term
Each of the numbers in the proportion is a term. They are numbered as follows.

7. The 1st and 4h terms are
the Extremes. The 2nd and
3rd terms are the Means.

8. The product of the means equals the product of the extremes.
Cross products are equal.
2 • 12 = 3 • 8
24 = 24

9. To Solve Proportions
Find n
9 n =
(3) (6)
9 n = 18
n = 2

10. use labels A car travels 60 mi / hr. How far can it travel in 7 hrs.?
60 mi = n mi
1 hr hrs.

11. 60 mi = n mi
1 hr hrs.
( 60 ) ( 7 ) = 1 n
420 mi. = n

12. Capture Recapture Method
Allows biologists to find
the number of animals or
fish in an area by estimating.

13. In a lake,
researchers caught, marked
and released 213 bass. Later,
they took a sample of 104 bass
13 were marked. Estimate
the total number of bass.

14. 13 213 = sample 104 x Marked sample Marked in lake = Total in sample
Total in lake = 13
104
213 x =
Lake
sample

15. 13
104
213 x =
13 x = ( 213) (104)
13 x = 22,152
x = 1704
Approx
bass in the lake

16. The desire to succeed means nothing without the will to prepare!
thought for the day
The desire
to succeed
means nothing
without the
will to prepare!