® Got It? 3. a. You row u p stream at a sp eed of 2 m i /h. You travel the sam e distance
dow nstream at a speed of 5 m i /h. W hat w ould be your rowing speed in
still w ater? W hat is th e sp ee d of th e current?
b. Reasoning Suppose your rowing speed in still w ater is 3 m i / h an d
the sp eed of the cu rren t is 4 m i /h. W hat h ap p e n s w hen you try to
row upstream?Lesso n Ch eck
Do y o u k n o w H OW?- N e w s le tte rs P rinting a new sletter costs $1.50 p er
copy plus $450 in p rin ter's fees. The copies are sold
for $3 each. How m any copies of th e new sletter m u st
be sold to break even? - Jewelry A m etal alloy is a m etal m ad e by blending
2 or m ore types of m etal. A jew eler has supplies of
two m etal alloys. One alloy is 30% gold an d th e other
is 10% gold. How m u ch of each alloy should the
jeweler com bine to create 4 kg of an alloy containing
15% gold? - Flying With a tailwind, a bird flew at a g round speed
of 3 m i/h. Flying th e sam e p a th against th e sam e
wind, the bird travels at a ground speed of 1.5 m i /h.
W hat is the b ird ’s air speed? W hat is th e w ind speed?
MATHEMATICAL
Do y o u UN DERSTAND? Jg JJ PRACTICES- Vocabulary W hat is th e relationship betw een
incom e an d expenses before a break-even p o in t is
reached? W hat is the relationship b etw een incom e
an d expenses after a break-even p o in t is reached? - Reasoning W hich m eth o d w ould you use to solve
th e following system? Explain.
3x + 2y = 9
-2x + 3y = 5
6. R e a s o n i n g One b ra n d of cranberry-apple drink is
15% cran b erry juice. A nother b ra n d is 40% cranberry
juice. You w ould like to com bine th e b ra n d s to
m ake a d rink th a t is 25% cran b erry juice. W ithout
calculating, w hich b ra n d of juice will you n e e d m ore
of to m ake your drink? Explain.Pr act i ce an d Pr o b l em - So l v i n g Ex er ci ses
Q P r a c t ic e
>3rMATHEMATICAL
PRACTICES- Business A bicycle store costs $2400 p er m o n th to operate. The store pays an 0 See Problem 1.
average of $60 p er bike. The average selling price of each bicycle is $120. How
m any bicycles m u st th e store sell each m o n th to b reak even? - T h e a t e r P roducing a m usical costs $88,000 plus $5900 p e r perform ance. One
sold-out p erform ance earns $7500 in revenue. If every p erform ance sells out,
how m any perform ances are n ee d ed to b reak even? - Investment You split $1500 betw een two savings accounts. Account A pays annual See Problem 2.
5% interest and Account B pays 4% annual interest. After one year, you have earned a
total of $69.50 in interest. How m uch m oney did you invest in each account? Explain.
^2*10. Biology A group of scientists studied th e effect of a chem ical on various strains
of bacteria. Strain A started with 6000 cells an d d ecreased at a co n stan t rate of
2000 cells p er h o u r after th e chem ical was applied. Strain B started w ith 2000 cells
an d d ecreased at a c o n stan t rate of 1000 cells p er h o u r after th e chem ical was
applied. W hen will the strains have the sam e n u m b e r of cells? Explain.
390 Chapter 6 Systems of Equations and Inequalities