Question

12 21×2.05

15 11×3.68

18 32×5.12

Explanation:

For \(21\times2.05\):

Step1: Expand 21 as (20 + 1)

\(21\times2.05=(20 + 1)\times2.05\)

Step2: Apply distributive property \(a\times(b + c)=a\times b+a\times c\)

\(=20\times2.05+1\times2.05\)

Step3: Calculate each product

\(20\times2.05 = 41\), \(1\times2.05=2.05\)

Step4: Add the results

\(41 + 2.05=43.05\)

For \(11\times3.68\):

Step1: Expand 11 as (10 + 1)

\(11\times3.68=(10 + 1)\times3.68\)

Step2: Apply distributive property

\(=10\times3.68+1\times3.68\)

Step3: Calculate each product

\(10\times3.68 = 36.8\), \(1\times3.68 = 3.68\)

Step4: Add the results

\(36.8+3.68 = 40.48\)

For \(32\times5.12\):

Step1: Expand 32 as (30+2)

\(32\times5.12=(30 + 2)\times5.12\)

Step2: Apply distributive property

\(=30\times5.12+2\times5.12\)

Step3: Calculate each product

\(30\times5.12=153.6\), \(2\times5.12 = 10.24\)

Step4: Add the results

\(153.6+10.24=163.84\)

Answer:

s:
\(21\times2.05=\boldsymbol{43.05}\)

\(11\times3.68=\boldsymbol{40.48}\)

\(32\times5.12=\boldsymbol{163.84}\)