Substituting into a formula

Question 1

If $a = 8$ and $b = - 4,$ which of following correctly evaluates $ab+ 7?$

Your answer is correct.

$ab + 7 = 8× - 4+ 7 = - 32+ 7 = - 25 .$

Not correct. Choice (b) is false.

Try again, you have calculated $a(b+ 7).$

Not correct. Choice (c) is false.

Try again, looking carefully at the signs.

Not correct. Choice (d) is false.

Try again, look carefully at the signs and the order of operations

Question 2

If $a = 2, b = - 3$ and $c = - 4,$ which of the following correctly evaluates $2a+ 3b- c?$

Not correct. Choice (a) is false.

Try again, remember this means $2a + 3b- c = 2 ×2 + 3× - 3- (- 4).$

Not correct. Choice (b) is false.

Try again, remember $- (- 4) = 4.$

Your answer is correct.

$2a + 3b - c = 2× 2 + 3× - 3 - (- 4) = 4- 9 + 4 = - 1.$

Not correct. Choice (d) is false.

Try again, look carefully at the signs.

Question 3

Suppose $z = x---μ. σ$
Which of the following is the value of $z$ if $x = 295 , μ = 310$ and $σ = 5?$

Not correct. Choice (a) is false.

Try again, looking carefully at the signs.

Your answer is correct.

$z = 295---310= - 15-= - 3. 5 5$

Not correct. Choice (c) is false.

Try again, you have not substituted into the formula correctly.

Not correct. Choice (d) is false.

Try again, you might have only divided one of the numbers by 5 getting $310 z = 295- -5- = 295- 62 = 233 .$

Question 4

Suppose $p - p z = ∘-Sp(1-p) -n---$ where $p = 0.04, pS = 0.05$ and $n = 500 .$
Which of the following gives the correct value for $z$ correct to 2 decimal places?

Not correct. Choice (a) is false.

Try again, you may not have noted that 1-0.04=0.96 and used 0.06, or used $p = 0.4$ and $pS = 0.5.$

Not correct. Choice (b) is false.

Try again, you have only divided 0.04 by the denominator, not 0.05-0.04.

Not correct. Choice (c) is false.

Try again, you have used $p = 0.4$ and $pS = 0.5$ and you have only divided 0.4 by the denominator, not 0.05-0.04 .

Your answer is correct.

$---0.05--0.04-- --0.01-- ---0.01---- -0.01--- z = ∘ 0.04(1--0.04) = ∘ 0.0384 = √0.0000768 = 0.00876 = 1.141. -----500---- -500--$

Question 5

Suppose $ˉx---μ z = σ∕√n-.$
Which of the following is the value of $z$ if $ˉx = 372.5, μ = 368, n = 25$ and $σ = 15?$

Not correct. Choice (a) is false.

Try again, look carefully at the signs.

Your answer is correct.

$372.5---368 4.5- 4.5 z = 15∕√25- = 15∕5 = 3 = 1.5.$

Not correct. Choice (c) is false.

Try again, you have not taken the square root of $n .$

Not correct. Choice (d) is false.

Try again, look carefully at the sign and you have not taken the square root of $n.$


		Faculty of Economics and Business MathQuiz