The abacus , also called a counting frame, is a calculating tool that was in use in Europe, China and Russia, centuries before the adoption of the written Hindu–Arabic numeral system.
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Nigeria, an African country on the Gulf of Guinea, has many natural landmarks and wildlife reserves. Protected areas such as Cross River National Park and Yankari National Park have waterfalls, dense rainforest, savanna and rare primate habitats. One of the most recognizable sites is Zuma Rock, a 725m-tall monolith outside the capital of Abuja that?s pictured on the national currency.

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