34
Multiplying numbers with a zero in the middle
Textbook: Part 1, lesson 34, pp. 105–107
GoalMultiply numbers with a zero in the middle; perimeter of a regular polygon.
New words
zero in the middle · o‘rtasida nolregular polygon · muntazam ko‘pburchakloan (credit) · kreditdeposit · omonat
Explanation
If a factor has a 0 in the middle, we skip the row for multiplying by 0: the product by the next place is written starting two places to the left of the first one. All sides of a regular polygon are equal, so its perimeter is the side length times the number of sides.
Worked examples
615 × 204 = 615 × 4 + 615 × 200 = 2 460 + 123 000 = 125 460; so 615 000 × 204 = 125 460 000.
A regular octagon with side 207 cm: P = 207 × 8 = 1 656 cm.
Class activity
“Skip the zero”: children write 305 × 4 218 in a column and show which row is left out and where the next product starts.
Practice
1
305 × 4 218 = ?
1286490
2
509 × 64 000 = ?
32576000
3
236 400 × 1 405 = ?
332142000
4
A tablet costs 3 950 000 so‘m in cash. On a 10-month loan it is paid at 415 000 so‘m a month. How many so‘m more is paid on the loan?
200000
5
A regular pentagon has side 503 cm. What is its perimeter in cm?
2515
6
If 3 200 000 so‘m is put into a deposit each month, how many so‘m is saved in 7 years (1 year = 12 months)?
268800000