When children understand comparison phrases such as "weighs more than", "weighs about the same as" and "weighs less than", and can print the letters of the alphabet, they can complete these weight problems.
You need a primary balance and 10 to 12 objects to weigh, such as an apple, a toy car or a golf ball, that will fit inside the buckets of the balance. This activity works best as a learning station. Place the objects to weigh near the balance. Each child should pick two objects, placing one in each of the buckets on the balance. They should determine which of the comparison phrases ("weighs more than", "weighs less than" or "weighs about the same as") is correct. Help younger students answer with a complete sentences, such as, "The apple weighs more than the toy car." Older students can answer by writing complete sentences.
For searching for lbs. and oz. you need a balance, a 1 lb. and a 1 oz. weight. Allow the students to pick up the 1 lb weight to get a sense of how much 1 lb. weighs. Tell them to search the classroom for objects they think might also weigh 1 lb. They should place the object on the balance to see if it weighs about 1 lb. For each object they weigh, they should write a number sentence comparing the object to the weight, using the symbols for greater than (>), less than (<) or equal to (=). For example, (weight of the object) > 1 lb. Repeat using 1 oz. objects.
When you stand on a scale and measure your weight, you are really measuring the force of attraction (gravity) between you and the earth. Your weight on other planets depends on the mass of the planet and your distance from the center of the planet. Sir Isaac Newton devised a formula for force that we can use to find how much we would weigh on another planet: Force = Your mass times the planet's mass divided by the square of your distance from the center of the planet. To make it easier, the planet's mass and distance² to the center of the planet have already been calculated for you.
Tell the students to find their weight on each planet by multiplying their weight by the decimal number following the name of the planet: Mercury (.38), Venus (.9), the earth's moon (.17), Mars (.38), Jupiter (2.34), Saturn (1.08), Uranus (.8), Neptune (1.12), and the dwarf "planet" Pluto (.05). Older students can find the difference between their weight on Earth and weight on other planets, or convert the weights to the metric system by multiplying lbs. by 2.2 to get kilograms.
Mixed customary weights use two customary units of weight to express a single measure, such as 2 lbs., 5 oz. Measures of mixed units are written in one of three ways: using both units (2 lbs. 5 oz.), using only the smaller unit (37 oz.) or using the larger unit and a fraction of that unit (2 5/16 lbs.). Have the students solve addition and subtraction problems involving mixed customary units of weight, expressing the answer all three ways.