Perform the calculation mentally
1. 90 + 247 + 253 + 110
2. 799 - 117
3. 25 × 25 × 8
3 answers
Never Mind My Bad :)
Think of ways to do them "in your head" without a pencil or calculator.
In #1, note that 90+110 = 200 and 243+257 = 500. Add 200 and 500.
#2 can be answered "on sight". No "carrying" is necessary.
#3. Note that 8x25 = 200
Multiply that by 25. The ones and tens columns remain zero.
In #1, note that 90+110 = 200 and 243+257 = 500. Add 200 and 500.
#2 can be answered "on sight". No "carrying" is necessary.
#3. Note that 8x25 = 200
Multiply that by 25. The ones and tens columns remain zero.
I "saw" #3 as
25 x 4 x 25 x 2 or 100x50
25 x 4 x 25 x 2 or 100x50