Question

*see answer key. the mental math section should not be duplicated for the students.
name maggie

1. $(27 + 4)-(8 \times 3)$
2. $2^4 + 3^2$
3. $25 \times 10 \times \frac{1}{25}$
4. $\frac{\sqrt{4}}{\sqrt{81}}$
5. $-100 \times -1$
6. $\frac{3}{5} - \frac{3}{10}$
7. $15 \times 2 - 45$
8. $-4(2)$
9. $5 \text{ cm} = \underline{\quad\quad} \text{ m}$
10. estimate: what percent of 51 is 32?

keeping skills sharp

Explanation:

Step1: Solve parentheses first

$(27+4)=31$, $(8×3)=24$
$31-24$

Step2: Subtract the values

$31-24=7$

Step1: Calculate exponents

$2^4=16$, $3^2=9$
$16+9$

Step2: Add the values

$16+9=25$

Step1: Simplify using multiplication properties

$25×\frac{1}{25}=1$
$1×10$

Step2: Multiply the values

$1×10=10$

Step1: Calculate square roots

$\sqrt{4}=2$, $\sqrt{81}=9$
$\frac{2}{9}$

Step1: Multiply negative numbers

$-100×-1=100$

Step1: Find common denominator

$\frac{3}{5}=\frac{6}{10}$
$\frac{6}{10}-\frac{3}{10}$

Step2: Subtract fractions

$\frac{6-3}{10}=\frac{3}{10}$

Step1: Multiply first

$15×2=30$
$30-45$

Step2: Subtract the values

$30-45=-15$

Step1: Multiply the values

$-4×2=-8$

Step1: Convert cm to meters

$1\ \text{m}=100\ \text{cm}$, so $5\ \text{cm}=\frac{5}{100}\ \text{m}$

Step2: Simplify the fraction

$\frac{5}{100}=0.05$

Step1: Set up percentage formula

$\text{Percent}=\frac{32}{51}×100$

Step2: Estimate the value

$\frac{32}{51}≈0.627$, $0.627×100≈63\%$ (or approximate to 60% as a simpler estimate)

Answer:

1. $7$
2. $25$
3. $10$
4. $\frac{2}{9}$
5. $100$
6. $\frac{3}{10}$
7. $-15$
8. $-8$
9. $0.05$
10. $\approx 60\%$ (or $\approx 63\%$ for a closer estimate)