Math Help

Archive for March, 2010

Question: To Math/Algebra Whiz Kids: Help! ?

Need ALGEBRA / Math Help – just with two questions!Two word problems! Please help?
Molly has $18.35 in coins; she has more nickels than dimes; she has seven fewer quarters than dimes. How many quarters does she have?

Kevin invested part of his $10,000 bonus in a certificate of deposit that paid 6% annual simple interest, and the remainder in a mutual fund that paid 11% annual simple interest. If his total interest for that year was $700, how much did he invest in the mutual fund?

Please help! I’ve tried the %x+%(original amount-x) = sum of interest on the last one, but I got x = 34,945… ?!

Answer: 1. Let x be the number of nickels, y be the number of dimes, and z be the number of quarters.

x>y
z=y-7
0.05x + 0.1y + 0.25z = 18.35 sub in z=y-7
0.05x + 0.1y + 0.25(y-7) = 18.35
0.05x + 0.1y + 0.25y – 1.75 = 18.35 now add 1.75 to both sides:
0.05x + 0.35y = 20.1 divide by 0.05
x + 7y = 402

This is as far as you pretty much can go with the information

2. Let x be the amount invested in the 6% intrest, and y be the amount invested in the 11% intrest

10000 = x + y rearrange for y
y = 10000 – x
0.06x + 0.11y = 700 sub in y = 10000 -x
0.06x + 0.11(10000 – x) = 700 simplify
0.06x + 1100 – 0.11x = 700 solve for x
-0.05x = -400
x = 8000
y = 10000 – x sub in x = 8000
y = 2000

Therefore he invested $8000 in the 6% mutual fund and $2000 in the 11% mutual fund.

Math Equations, Fractions & Problem Solving : Math Help for Parents

Question: a confusion in Integration maths?

integrate (x^2+1)^5

(maybe writing it down will help

Answer: /
either expand or use trig sub
x=tany
dx=sec^2ydy
sub
intsec^7ydy
use
sec^n(y)dy=1/(n-1)*sec^(n-2)xtanx+
(n-2)/(n-1)*intsec^(n-2)xdx

Integration by Parts

Question: I need help with a math problem (percent raise)?

I need help with a math problem (percent raise)
Question Details:In one month you had both a raise and a $250 bonous for exceeding your goals by 10%. Your old paycheck gross was $2,300, with a net pay of $1,791. This month your paycheck was $2,711.

How much was your raise?

Answer: 2300 * .07 = 161
161 + 250 = 411
411 + 2300 = 2711
so it’s 7%

Percent to Decimal – YourTeacher.com – Math Help