Posted by rebeca on Tuesday, October 2, 2007 at 12:32pm.
alter working 4 hours, frank has made 21 machine parts.at the same rate how many parts can he make in 7 hours? 4(21)/7,7(21),7(21)/4,7(4)/21,7(4)(21)?

math  Ms. Sue, Tuesday, October 2, 2007 at 12:34pm
Please post your answer and we'll be glad to check it.

math  rebeca, Tuesday, October 2, 2007 at 1:09pm
i choose a)4(21)/7

math  DrBob222, Tuesday, October 2, 2007 at 12:36pm
Look at dimensional analysis.
21 parts/4 hrs x ?hrs = ?parts. 
math  Ms. Sue, Tuesday, October 2, 2007 at 1:13pm
How can a) be the right answer? 4(21)/7 = 12. The problem has stated that he made 21 parts in 4 hours. How can he make fewer parts in more hours?
Please try again.
Hint: you could set up a proportion:
4 is to 21 as 7 is to x 
math  rebeca, Tuesday, October 2, 2007 at 1:23pm
d)7(4)/21

math  Ms. Sue, Tuesday, October 2, 2007 at 1:27pm
7(4)/21.
Do the math. Does the answer make sense?