Estimate sums: :
use rounding or compatible numbers to estimate the sum.
222
+
203

225

Step-by-step explanation:

The rounding system is used by rounding the numbers so by rounding the method would be:

And compatible numbers would be rounding to the nearest five:

So the compatible numbers gives you the exact answer but it´s not always this way.

b) 1/3 * 1/5

step-by-step explanation:

each smallest part is 1/15 since the written one is 1/5 and it's divided by 3 equal parts. (1/5 )/3 = 1/15 = 1/3 * 1/5

8+10

step-by-step explanation:

you multiply 4 by 2 and 5 by 2