Pure gold is often mixed with other metals to produce jewelry. Pure gold is 24 carat. 12 carat gold is 12/24 or 50% gold, 6 carat gold is 6/24 or 25% gold, etc. A jeweler has some 12 carat gold and some 21 carat gold and wants to produce 90 g of 75% gold. a. What percentage of gold is 21 carat?

b. How many grams of 12 carat gold and 21 carat gold are needed to produce the mixture?

a. 87.5%

b. 30 g of 12 carat and 60 g of 21 carat.

Step-by-step explanation:

a. The percentage of gold in 21 carat is given by:

b. Since the mass he wants to produce is 90 g, then the added mass of the 12 carat, "x", and the mass of the 21 carat "y", must be equal to that:

The sum of gold on each carat type must be equal to the amount of gold on the final mixture, since a 12 carat has 50% gold and a 21 carat has 87.5% gold, then we have:

We now have a system of equations which we can solve to find the necessary mass of each type.

He needs 30 g of 12 carat gold and 60 g of 21 carat gold.

geometric series converge the common ratio r has magnitude less than one.

which is equivalent to

for the example we need

|2-x| < 1

-1 < 2-x   and 2-x < 1

x < 3 and x > 1

we can write that

answer: 1 < x < 3

1a. common ratio r=250/25=10 > 1     diverges

1b.   r=50/100=1/2 converges

when these converge they converge to

where a is the first term.

answer: 200

1c. r=-1   so it's not the case that |r| < 1.     diverges

2a. x is the common ratio so we converge when |x|< 1

2b.   r=-10x / -2 = 5x.

we converge when

|5x| < 1

|x| < 1/5

2c.   r=3-2x

-1 < 3-2x and 3-2x < 1

-4 < -2x and 2 < 2x

x < 2 and 1 < x

1 < x < 2

2d. [/tex] r=-48x^3/12 = 4x^3[/tex]

|4x^3| < 1

|x^3| < \frac 1 4

|x| < 4^{-1/3}

15%

step-by-step explanation:

use the table and count the number of guesses that has two correct answers.

the following are two correct answers

10010, 01100, 11000

a total of 3 numbers having 2 correct guesses out of 20 questions.

probability of getting 2 correct guesses = the number of questions getting 2 correct answers / total number of questions.

= 3/20

to convert it into percent multiply by 100, we get

= 3/20 * 100

= 15%

the answer is 15%

you.