2006-10-21 01:59:07 · 16 answers · asked by its just me 3 in Science & Mathematics ➔ Mathematics
The most elegant way to do this is look at the factors.
35 = 5 x 7 and 18 = 3 x 6,
Number of students in the school is clearly the product of those 4 factors.
i.e. (5 x 7) x (3 x 6)
But noticing that 5 x 6 is 30 (the new class size) it becomes intuitively obvious that the new number of classrooms must be 3 x 7 = 21.
We have 18 already, and therefore need 3 more.
No multiplication and division is necessary. once you spot this pattern, as multiplication is commutative:
(5 x 7) x (3 x 6) gives the same result as
(5 x 6) x (3 x 7) and you DON'T need to work out that that is 630 and then divide it by 30 to get 21.
NB This habit of spotting the factors helps mental arithmetic; knowing that 12 x 12 = 144, for example, means you can see at a glance that 8 x 18 must also = 144 as must 16 x 9 and don't need to multiply to arrive at that result.
2006-10-21 02:36:21 · answer #1 · answered by Anonymous · 14⤊ 1⤋
Total number of students = 18 class x 35 student = 630 students
To reduce the class to 30 we require 630/30 = 21 class
we already have 18 class
so we require 21 - 18 = 3 class.
2006-10-21 05:36:34 · answer #2 · answered by Venkatesh V S 5 · 0⤊ 0⤋
18*35= 630 students total. To reduce the class size to 30, you divide 630 by 30 to get 21 classes. Then you subtract 18 from 21 to get 3 new classes.
2006-10-21 04:42:53 · answer #3 · answered by cheesy 2 · 0⤊ 0⤋
3
2006-10-21 03:08:06 · answer #4 · answered by Anonymous · 0⤊ 0⤋
3
2006-10-21 02:07:07 · answer #5 · answered by Anonymous · 0⤊ 0⤋
Total Number of Students: 18 x 35 = 630
Number of classes of 30 students needed =630/30 = 21
New Classes added = 21 -18 = 3.
2006-10-21 02:44:12 · answer #6 · answered by Anonymous · 1⤊ 0⤋
18 classes with 35 students each.
Total number of students =
18 X 35 = 630 students
to achieve 30 students in each class:
630/30 = 21 classes
Therefore number of new classes =
21 - 18 = 3 new classes
2006-10-21 05:14:30 · answer #7 · answered by Loral 2 · 0⤊ 0⤋
new classes with 30
=18*35/30=21
additional classes
=21-18=3
2006-10-21 04:40:02 · answer #8 · answered by openpsychy 6 · 0⤊ 0⤋
-5 from 35 =30 new class size
18 x 5 = 80 students
30 + 30 + 20 =3 classes with only 20 in the 3rd class
2006-10-21 02:13:39 · answer #9 · answered by Anonymous · 0⤊ 0⤋
18 classes with 35 students
Total students will be 18*35=630
If each class were to have 30 students, they'll need 630/30=21 classes
Additional classes needed will be 21-18=3
The school will need 3 new classes.
2006-10-21 02:49:44 · answer #10 · answered by kenyanmartin2000 2 · 1⤊ 0⤋