استخدم الحساب الذهني لإيجاد مجموع الأعداد التالية :
1) 17 + 28 + 23
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2) 42 + 0 + 18
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3) 35 + 16 + 4
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1) 4 × 17 × 25
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2) 80 × 25 × 12
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3) 35 × 2 × 7
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1) 17 + 28 + 23
.............................................................
.............................................................
.............................................................
2) 42 + 0 + 18
.............................................................
.............................................................
.............................................................
3) 35 + 16 + 4
.............................................................
.............................................................
.............................................................
1) 4 × 17 × 25
.............................................................
.............................................................
.............................................................
2) 80 × 25 × 12
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.............................................................
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3) 35 × 2 × 7
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