Answer
1. \(-0.6\)
2. \( \frac{55}{14} \) or approximately **3.9286**
3. \(-18.9\)
4. \(-1.56\)
5. \(-5.9\)
6. **0.7**
7. **3.45**
8. **6.9**
Solution
Sure! Let's evaluate each of the given mathematical expressions step by step.
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### **1.** \( -0.8 + \frac{1}{9} \times 1 \frac{4}{5} \)
**Step 1:** Convert the mixed number to an improper fraction.
\[ 1 \frac{4}{5} = \frac{9}{5} \]
**Step 2:** Multiply \(\frac{1}{9}\) by \(\frac{9}{5}\).
\[ \frac{1}{9} \times \frac{9}{5} = \frac{9}{45} = \frac{1}{5} = 0.2 \]
**Step 3:** Add the result to \(-0.8\).
\[ -0.8 + 0.2 = -0.6 \]
**Answer:** \(-0.6\)
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### **2.** \( 2.5 - 1 \frac{2}{3} \times \left(-\frac{6}{7}\right) \)
**Step 1:** Convert the mixed number to an improper fraction.
\[ 1 \frac{2}{3} = \frac{5}{3} \]
**Step 2:** Multiply \(\frac{5}{3}\) by \(-\frac{6}{7}\).
\[ \frac{5}{3} \times \left(-\frac{6}{7}\right) = -\frac{30}{21} = -\frac{10}{7} \approx -1.4286 \]
**Step 3:** Subtract the product from 2.5.
\[ 2.5 - (-1.4286) = 2.5 + 1.4286 = 3.9286 \]
**Answer:** \( \frac{55}{14} \) or approximately **3.9286**
---
### **3.** \( -4.9 \div [0.3 - (-0.4)] \times 2.7 \)
**Step 1:** Simplify inside the brackets.
\[ 0.3 - (-0.4) = 0.3 + 0.4 = 0.7 \]
**Step 2:** Perform the division.
\[ -4.9 \div 0.7 = -7 \]
**Step 3:** Multiply by 2.7.
\[ -7 \times 2.7 = -18.9 \]
**Answer:** \(-18.9\)
---
### **4.** \( 3.25 \div (-1.7 - 0.8) \times 1.2 \)
**Step 1:** Simplify the denominator.
\[ -1.7 - 0.8 = -2.5 \]
**Step 2:** Perform the division.
\[ 3.25 \div (-2.5) = -1.3 \]
**Step 3:** Multiply by 1.2.
\[ -1.3 \times 1.2 = -1.56 \]
**Answer:** \(-1.56\)
---
### **5.** \( -0.6 \times 2 \frac{1}{3} - 4 \div \frac{8}{9} \)
**Step 1:** Convert the mixed number to an improper fraction.
\[ 2 \frac{1}{3} = \frac{7}{3} \]
**Step 2:** Multiply \(-0.6\) by \(\frac{7}{3}\).
\[ -0.6 \times \frac{7}{3} = -1.4 \]
**Step 3:** Perform the division.
\[ 4 \div \frac{8}{9} = 4 \times \frac{9}{8} = \frac{36}{8} = 4.5 \]
**Step 4:** Subtract the results.
\[ -1.4 - 4.5 = -5.9 \]
**Answer:** \(-5.9\)
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### **6.** \( 3.5 \times \left(-\frac{1}{7}\right) + \frac{3}{4} \div \frac{5}{8} \)
**Step 1:** Multiply \(3.5\) by \(-\frac{1}{7}\).
\[ 3.5 \times \left(-\frac{1}{7}\right) = -0.5 \]
**Step 2:** Perform the division.
\[ \frac{3}{4} \div \frac{5}{8} = \frac{3}{4} \times \frac{8}{5} = \frac{24}{20} = 1.2 \]
**Step 3:** Add the results.
\[ -0.5 + 1.2 = 0.7 \]
**Answer:** **0.7**
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### **7.** \( 3 \frac{1}{4} - (-0.18) \div \left(\frac{1}{5} + 0.7\right) \)
**Step 1:** Convert the mixed number to a decimal.
\[ 3 \frac{1}{4} = 3.25 \]
**Step 2:** Simplify the denominator.
\[ \frac{1}{5} + 0.7 = 0.2 + 0.7 = 0.9 \]
**Step 3:** Perform the division.
\[ -0.18 \div 0.9 = -0.2 \]
**Step 4:** Subtract the result.
\[ 3.25 - (-0.2) = 3.25 + 0.2 = 3.45 \]
**Answer:** **3.45**
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### **8.** \( 7 \frac{2}{5} - \left(-3 \frac{1}{2}\right) \div (-9 + 2) \)
**Step 1:** Convert mixed numbers to decimals.
\[ 7 \frac{2}{5} = 7.4 \]
\[ -3 \frac{1}{2} = -3.5 \]
**Step 2:** Simplify the denominator.
\[ -9 + 2 = -7 \]
**Step 3:** Perform the division.
\[ \left(-3.5\right) \div (-7) = 0.5 \]
**Step 4:** Subtract the result.
\[ 7.4 - 0.5 = 6.9 \]
**Answer:** **6.9**
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