Share and discuss in class the different methods each of you used to solve these questions. Class 6

Share and discuss in class the different methods each of you used to solve these questions. Class 6

Question 1.

Share and discuss in class the different methods each of you used to solve these questions. Class 6

Solution:

We use a quicker wai in each case. Do as directed

(a) Sum = 40 × 4 + 50 × 5 + 40 × 4 + 50 × 5 + 40 × 4

= 160 + 250 + 160 + 250 + 160

= 160 × 3 + 250 × 2

= 480 + 500 = 980.

(b) Sum = 1 × 8 + 1 × 4 + 5 × 4 + 1 × 4 + 5 × 4 + 1 × 6 + 5 × 2 + 1 × 6 + 5 × 2 + 1 × 4 + 5 × 4 + 1 × 4 + 5 × 4 + 1 × 8

= 8 + 4 + 20 + 4 + 20 + 6 + 10 + 6 + 10 + 4 + 20 + 4 + 20 + 8

= 8 × 2 + 4 × 4 + 20 × 4 + 6 × 2 + 10 × 2

= 16 + 16 + 80 + 12 + 20

= 32 + 80 + 32

= 32 × 2 + 80

= 64 + 80 = 144.

(c) Sum = 32 × 32 + 64 × 16

= 1024 + 1024

= 1024 × 2 = 2048.

(d) Sum = 3 × 7 + 4 × 6 + 3+ 4 × 6 + 3 + 4 × 6 + 3 + 3 × 7

= 21 + 24 + 3 × 3 + 24 + 24 + 21

= 21 × 2 + 24 × 3 + 9

= 42 + 72 + 9

= 114 + 9 = 123.

Or sum may be 18 × 6 + 3 × 5

= 108 + 15 = 123.

(e) Sum = 15 × 4 + 35 × 6 + 25 × 4 + 25 × 6 + 35 × 4 + 15 × 6+ 25 × 4 + 35 × 6 + 15 × 4 + 25 × 6 + 35 × 4 + 15 × 6 + 15 × 1 + 25 × 1 + 35 × 225 × 1 + 15 × 1

= 15 × 22 + 35 × 22+ 25 × 22

= 330 + 770 + 550 = 1650.

(f) Sum = 1000 × 1 + 500 × 4 + 250 × 8 + 125 × 18

= 1000 + 2000+ 2000 + 2250

= 7250.