10x3=30 (ml)

30x3=90 ml

90 & lt 120

A: This bottle of cough syrup is enough for a five-year-old child to take for three days.

Question: How many days does an 8-year-old child need to take this bottle of cough syrup? (The problem is not unique)

15x3=45 (ml)

120÷45=2 (days) ... 30ml

A: The minimum dose of this bottle of cough syrup is enough for an 8-year-old child to take for 2 days.

analyse

This topic examines how to solve problems by multiplication and division.

By observing the specifications and dosage chart of cough syrup, we can know that when children aged 3-7 drink 5- 10 ml each time, the maximum amount that children aged 5 drink three times a day is 10x3=30 ml, and the maximum amount that children drink three days is 30x3=90 ml, 90.

How many days does this bottle of cough syrup last for an 8-year-old child? Every bottle 120ml, children over 7 years old should drink at least 15ml each time, 15x3 = 45ml three times a day, 120÷45=2 (days) ... 30 (ml), which is enough for an 8-year-old child.

Extended data:

A clever way to apply problems:

First, the application problem needs to transform the text description in the topic into a mathematical formula; Second, in the face of a lot of text information in the topic, children often can't grasp where the key information is; Third, the child just started to contact the application problem, did not develop the good habit of doing the problem, did not pay attention to what the question asked, and began to write and do, often in the opposite direction; Fourth, children don't pay attention to writing habits, don't bring units, don't answer, don't check, and often lose points in exams.