Solving Math 5 exercises on page 77 Practice Workbook

Guidelines for solving 5th Grade Math exercises on page 77 Practice (including solving methods)

Solve Exercise 1 - Math for 5th Grade practice page 77

Problem:
a) Find 15% of 320kg;                  b) Find 24% of 235m²;                           c) Find 0.4% of 350;

Solution Method:
To find a% of b, we divide b by 100 and then multiply by a; alternatively, we can multiply b by a and then divide by 100. 

Answer:
a) 15% of 320kg is :                     b) 24% of 235m² is:                                c) 0.4% of 350 is:
    320 : 100 x 15 = 48(kg)                   235 : 100 x 24 = 56.4(m²)                         350 : 100 x 0.4 = 1.4.

2.Solve Exercise 2 - Math 5 page 77 practice

Problem:
A rice seller has 120 kilograms of rice, of which 35% is sticky rice. How many kilograms of sticky rice did the seller sell?

Solution Method:
To find out how many kilograms of sticky rice the seller sold, we multiply the total kilograms of rice sold by 35% (or divide the total kilograms of rice sold by 100, then multiply by 35). 

Answer:
              The seller has sold:
                              120 : 100 x 35 = 42(kg)
                                      Answer: 42kg.

3. Solve Exercise 3 - Math 5 page 77 practice

Problem:
A rectangular piece of land has a length of 18m and a width of 15m. 20% of the land area is used to build a house. Calculate the area of the land used for building the house.

Solution Method:
- Calculate the area of the rectangular piece of land by multiplying the length by the width
- Calculate the area of the land used for building the house by multiplying the land area by 20% (divide by 100, then multiply by 20). 

Answer:
          The area of the land is:
                 18 x 15 = 270(m²)
         The area of the land used for building the house is:
                  270 : 100 x 20 = 54(m²)
                            Answer: 54m²

4. Solving Exercise 4 Math 5 page 77 practice

Problem:
A fruit garden has 1200 trees. Calculate mentally 5%, 10%, 20%, 25% of the number of trees in the garden.

Solution Method:
1. First Mental Calculation Method
- Step 1: Find 1% of the number of trees in the garden by dividing the total number of fruit trees in the garden by 100
- Step 2: Find a%, b%, c%,... of the number of trees in the garden by multiplying 1% of the number of trees in the garden (obtained above) by a, b, c,...
2. Second Mental Calculation Method
Write the given percentages as fractions and calculate the corresponding number of trees by multiplying the total number of trees by the found fraction (corresponding to the given percentage).

So: 5% of the trees is: 1200 : 20 = 60 (trees)
      10% of the trees is: 1200 : 10 = 120 (trees)
      20% of the trees is: 1200 : 5 = 240 (trees)
      25% of the trees is: 1200 : 4 = 300 (trees).

Guide to solving Grade 5 math exercise page 77 (concise)

Find 15% of 320. Solution: 320 x 15 : 100 = 48 (kg).

A rectangular piece of land has dimensions 18m by 15m. 20% of the area is used for building a house. Find the area of the land used for the house. Solution: Area of land = 18 x 15 = 270 (m2), Area for house = 270 x 20 : 100 = 54 (m2).

Calculate 5%, 10%, 20%, 25% of 1200 trees in an orchard. Solution: 5% = 60 trees, 10% = 120 trees, 20% = 240 trees, 25% = 300 trees.

For further practice, explore multiplying decimals. This prepares for upcoming lessons in the 5th-grade Math curriculum.

End of exercises.

Prepare for the next topic on percentage ratios by solving exercises from page 78 and practice from page 79 in the 5th-grade Math textbook.