$$\frac{9.8}{0.120}$$ - 

$$100$$

$$\frac{98}{0.111}$$ - 

$$1000$$

$$\frac{9.8}{0.2003}$$ - 

$$50$$

$$\frac{980}{0.199}$$ - 

$$5000$$

$$\frac{980}{0.498}$$ - 

$$2000$$

$$\frac{9}{0.51}$$ - 

$$18$$

38.48 + 29.84 - 

$$\approx$$ 40 + 30

18.983 + 19.303 - 

$$\approx$$ 20 + 20

45.9348 + 39.84 - 

$$\approx $$ 50 + 40

8.548 + 2.84 + 19.203 - 

$$\approx$$ 9 + 3 + 20

38.48² + 29.84 - 

$$\approx$$ 40² + 30

$$\approx \text{ }$$8 × 8 - 

Area of a square with lengths 7.89 m

$$\approx \text{ }$$8 + 8 + 8 + 8 - 

Perimeter of a square with lengths 7.89 m

$$\approx\text{ }$$ 5 × 5 - 

Area of a square with lengths 4.67 m

$$\approx \text{ }$$ 5 + 5 + 5 + 5 - 

Perimeter of a square with lengths 4.67 m

$$\approx\text{ }$$ 0.5 × 0.5 - 

Area of a square with lengths 0.498 m

$$\approx\text{ }$$0.5 + 0.5 + 0.5 + 0.5 - 

Perimeter of a square with lengths 0.498 m

Overestimate - 

$$\frac{899}{4.40+6.35}\approx\frac{900}{4+6}$$

Underestimate - 

$$\frac{712}{8.98+9.45}\approx\frac{700}{10+10}$$

Hard to tell - 

$$\frac{37.4}{4.49+6.41}\approx\frac{40}{5+6}$$

Overestimate - 

$$\frac{59-42}{3.67+1.23}\approx\frac{60-40}{3+1}$$

Underestimate - 

$$\frac{59-42}{3.67+1.23}\approx\frac{55-45}{4+2}$$

Hard to tell - 

$$\frac{59-42}{3.67+1.23}\approx\frac{60-50}{4+2}$$